1
Features
Monolithic Field Programmable System Level Integrated Circuit (FPSLIC)
AT40K SRAM-based FPGA with Embedded High-performance RISC AVR® Core and
Extensive Data and Instruction SRAM
5,000 to 40,000 Gates of Patented SRAM-based AT40K FPGA with FreeRAM
2 - 18.4 Kbits of Distributed Single/Dual Port FPGA User SRAM
High-performance DSP Optimized FPGA Core Cell
Dynamically Reconfigurable In-System FPGA Configuration Access Available
On-chip from AVR Microcontroller Core to Support Cache Logic® Designs
Very Low Static and Dynamic Power Consumption Ideal for Portable and
Handheld Applications
Patented AVR Enhanced RISC Architecture
120+ Powerful Instructions Most Single Clock Cycle Execution
High-performance Hardware Multiplier for DSP-based Systems
Approaching 1 MIPS per MHz Performance
C Code Optimized Architecture with 32 x 8 General-purpose Internal Registers
Low-power Idle, Power-save, and Power-down Modes
100 µA Standby and Typical 2-3 mA per MHz Active
Up to 36 Kbytes of Dynamically Allocated Instruction and Data SRAM
Up to 16 Kbytes x 16 Internal 15 ns Instructions SRAM
Up to 16 Kbytes x 8 Internal 15 ns Data SRAM
AVR Fixed Peripherals
Industry-standard 2-wire Serial Interface
Two Programmable Serial UARTs
Two 8-bit Timer/Counters with Separate Prescaler and PWM
One 16-bit Timer/Counter with Separate Prescaler, Compare, Capture
Modes and Dual 8-, 9- or 10-bit PWM
Support for FPGA Custom Peripherals
AVR Peripheral Control 16 Decoded AVR Address Lines Directly Accessible
to FPGA
FPGA Macro Library of Custom Peripherals
16 FPGA Supplied Internal Interrupts to AVR
Up to Four External Interrupts to AVR
8 Global FPGA Clocks
Two FPGA Clocks Driven from AVR Logic
FPGA Global Clock Access Available from FPGA Core
Multiple Oscillator Circuits
Programmable Watchdog Timer with On-chip Oscillator
Oscillator to AVR Internal Clock Circuit
Software-selectable Clock Frequency
Oscillator to Timer/Counter for Real-time Clock
VCC: 3.0V - 3.6V
3.3V 33 MHz PCI Compliant FPGA I/O
20 mA Sink/Source High-performance I/O Structures
All FPGA I/O Individually Programmable
High-performance, Low-power 0.35µ CMOS Five-layer Metal Process
State-of-the-art Integrated PC-based Software Suite including Co-verification
Description
The AT94K Series (FPSLIC family) shown in Table 1 is a combination of the popular
Atmel AT40K Series SRAM FPGAs and the high-performance Atmel AVR 8-bit RISC
microcontroller with standard peripherals. Extensive data and instruction SRAM as
well as device control and management logic are included on this monolithic device,
fabricated on Atmels 0.35µ five-layer metal CMOS process.
Rev. 1138D09/01
5K - 40K Gates
of AT40K FPGA
with 8-bit
Microcontroller
and up to 36K
Bytes of SRAM
AT94K Series
Field
Programmable
System Level
Integrated
Circuit
AT94K Family
2
The AT40K FPGA core is a fully 3.3V PCI-compliant, SRAM-based FPGA with distributed 10 ns programmable synchro-
nous/asynchronous, dual-port/single-port SRAM, 8 global clocks, Cache Logic ability (partially or fully reconfigurable
without loss of data) and 5,000 to 40,000 usable gates.
Table 1. The AT94K Series
Device AT94K05AL AT94K10AL AT94K40AL
FPGA Gates 5 Kbytes 10 Kbytes 40 Kbytes
FPGA Core Cells 256 576 2304
FPGA SRAM Bits 2048 4096 18432
FPGA Registers (Total) 436 846 2862
Max FPGA User I/O 96 144 288
AVR Programmable I/O Lines 8 16 16
Program SRAM Bytes 4 Kbytes - 16 Kbytes 20 Kbytes - 32 Kbytes 20 Kbytes - 32 Kbytes
Data SRAM Bytes 4 Kbytes - 16 Kbytes 4 Kbytes- 16 Kbytes 4 Kbytes - 16 Kbytes
Hardware Multiplier (8-bit) Yes Yes Yes
2-wire Serial Interface Yes Yes Yes
UARTs 222
Watchdog Timer Yes Yes Yes
Timer/Counters 3 3 3
Real-time Clock Yes Yes Yes
Typical AVR throughput @ 25 MHz 19 MIPS 19 MIPS 19 MIPS
@ 40 MHz 30 MIPS 30 MIPS 30 MIPS
Operating Voltage 3.0 - 3.6V 3.0 - 3.6V 3.0 - 3.6V
AT94K Family
3
Figure 1. AT94K Architecture
The embedded AVR core, by executing powerful instructions in a single-clock-cycle, achieves throughputs approaching
1 MIPS per MHz allowing system designers to optimize power consumption versus processing speed. The AVR core is
based on an enhanced RISC architecture that combines a rich instruction set with 32 general-purpose working registers.
All 32 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing two independent registers to be
accessed in one single instruction executed in one clock cycle. The resulting architecture is more code-efficient while
achieving throughputs up to ten times faster than conventional CISC microcontrollers at the same clock frequency. The
AVR executes out of on-chip SRAM. Both the FPGA configuration SRAM and AVR instruction code SRAM can be automat-
ically loaded at system power-up using Atmels in-system programmable AT17 Series EEPROM configuration memories.
State-of-the-art FPSLIC design tools, System Designer, were developed in conjunction with the FPSLIC architecture to
help reduce overall time-to-market by integrating microcontroller development and debug, FPGA development and place
and route and complete system co-verification in one easy-to-use software tool.
5 - 40K Gates FPGA
Up to
4K x 8
Data
SRAM*
Up to 16K x 16
Program
SRAM Memory*
PROGRAMMABLE I/O
with
Multiply. Two 8-bit
Timer/Counters
16 Prog. I/O
Lines
I/O
I/O
I/O
2-wire Serial
Unit
Up to 16 Interrupt Lines
16 Addr
Decoder
4 Interrupt Lines
AT94K Family
4
Internal Architecture
Section 1 FPGA Core, page 5
Section 2 FPGA/AVR Interface and System Control, page 21
Section 3 AVR Core and Peripherals, page 33
Instruction Set Nomenclature, page 33
Pin Descriptions, page 39
Clock Options, page 41
Architectural Overview, page 42
AT94K Register Summary, page 47
Reset and Interrupt Handling, page 57
Timer/Counters, page 65
Watchdog Timer, page 84
Multiplier, page 85
UARTs, page 99
2-wire Serial Interface (Byte Oriented), page 110
I/O Ports, page 126
Section 4 AC and DC Characteristics, page 139
Section 5 Packaging and Pin List Information, page 148
AT94K Family
5
Section 1 FPGA Core
The AT40K core can be used for high-performance designs, by implementing a variety of compute-intensive, arithmetic
functions. These include adaptive finite impulse response (FIR) filters, fast Fourier transforms (FFT), convolvers, interpola-
tors, and discrete-cosine transforms (DCT) that are required for video compression and decompression, encryption,
convolution and other multimedia applications.
Fast, Flexible and Efficient SRAM
The AT40K core offers a patented distributed 10 ns SRAM capability where the RAM can be used without losing logic
resources. Multiple independent, synchronous or asynchronous, dual-port or single-port RAM functions (FIFO, scratch pad,
etc.) can be created using Atmels macro generator tool.
Fast, Efficient Array and Vector Multipliers
The AT40K cores patented 8-sided core cell with direct horizontal, vertical and diagonal cell-to-cell connections implements
ultra fast array multipliers without using any busing resources. The AT40K cores Cache Logic capability enables a large
number of design coefficients and variables to be implemented in a very small amount of silicon, enabling vast improve-
ment in system speed.
Cache Logic Design
The AT40K FPGA core is capable of implementing Cache Logic (dynamic full/partial logic reconfiguration, without loss of
data, on-the-fly) for building adaptive logic and systems. As new logic functions are required, they can be loaded into the
logic cache without losing the data already there or disrupting the operation of the rest of the chip; replacing or comple-
menting the active logic. The AT40K FPGA core can act as a reconfigurable resource within the FPSLIC environment.
Automatic Component Generators
The AT40K is capable of implementing user-defined, automatically generated, macros; speed and functionality are
unaffected by the macro orientation or density of the target device. This enables the fastest, most predictable and efficient
FPGA design approach and minimizes design risk by reusing already proven functions. The Automatic Component Gener-
ators work seamlessly with industry-standard schematic and synthesis tools to create fast, efficient designs.
The patented AT40K architecture employs a symmetrical grid of small yet powerful cells connected to a flexible busing
network. Independently controlled clocks and resets govern every column of four cells. The FPSLIC device is surrounded
on three sides by programmable I/O.
Core usable gate counts range from 5,000 to 40,000 gates and 436 to 2,864 registers. Pin locations are consistent through-
out the FPSLIC family for easy design migration in the same package footprint.
The Atmel AT40K FPGA core architecture was developed to provide the highest levels of performance, functional density
and design flexibility. The cells in the FPGA core array are small, efficient and can implement any pair of Boolean functions
of (the same) three inputs or any single Boolean function of four inputs. The cells small size leads to arrays with large num-
bers of cells. A simple, high-speed busing network provides fast, efficient communication over medium and long distances.
AT94K Family
6
The Symmetrical Array
At the heart of the Atmel FPSLIC architecture is a symmetrical array of identical cells. The array is continuous from one
edge to the other, except for bus repeaters spaced every four cells (See The Busing Network ). At the intersection of each
repeater row and column is a 32 x 4 RAM block accessible by adjacent buses. The RAM can be configured as either a sin-
gle-ported or dual-ported RAM, with either synchronous or asynchronous operation.
The Busing Network
Figure 2 depicts one of five identical FPGA busing planes. Each plane has three bus resources: a local-bus resource (the
middle bus) and two express-bus resources. Bus resources are connected via repeaters. Each repeater has connections to
two adjacent local-bus segments and two express-bus segments. Each local-bus segment spans four cells and connects to
consecutive repeaters. Each express-bus segment spans eight cells and leapfrogs or bypasses a repeater. Repeaters
regenerate signals and can connect any bus to any other bus (all pathways are legal) on the same plane. Although not
shown, a local bus can bypass a repeater via a programmable pass gate allowing long on-chip tri-state buses to be
created. Local/local turns are implemented through pass gates in the cell-bus interface (see following page).
Express/Express turns are implemented through separate pass gates distributed throughout the array.
= I/O Pad
= AT40K Cell
= Repeater Row
= Repeater
= RAM Block
Interface to AVR
AT94K Family
7
Figure 2. Busing Plane (one of five)
Cell Connections
Figure 3(a) depicts direct connections between an FPGA cell and its eight nearest neighbors. Figure 3(b) shows the
connections between a cell five horizontal local buses (one per busing plane) and five vertical local buses (one per busing
plane).
= Local/Local or Express/Express Turn Point
= AT40K Core Cell
= Row Repeater
= Column
AT94K Family
8
Figure 3. Cell Connections
(a) Cell-to-Cell Connections (b) Cell-to-Bus Connections
W
X
Y
Z
L
WXYZL
Y
X
Y
Y
Y
X
XX
CELL CELL CELL
CELL CELL CELL
CELL CELL CELL
CELL
AT94K Family
9
The Cell
Figure 4 depicts the AT40K FPGA embedded core logic cell. Configuration bits for separate muxes and pass gates are
independent. All permutations of programmable muxes and pass gates are legal. Vn is connected to the vertical local bus
in plane n. Hn is connected to the horizontal local bus in plane n. A local/local turn in plane n is achieved by turning on the
two pass gates connected to Vn and Hn. Up to five simultaneous local/local turns are possible.
The logic cell can be configured in several modes. The logic cell flexibility makes the FPGA architecture well suited to all
digital design application areas (see Figure 5). The IDS layout tool automatically optimizes designs to utilize the cell
flexibility.
Figure 4. The Cell
OUT OUT
RESET/SET
CLOCK
FB
X = Diagonal Direct Connect or Bus
Y = Orthogonal Direct Connect or Bus
W = Bus Connection
Z = Bus Connection
FB = Internal Feedback
10
Z
D
Q
"1" NW NE SE SW "1"
"1"
"1""0"
XWY
XZWY
"1" N E S W
8 X 1 LUT 8 X 1 LUT
XY
NW NE SE SW N E S W
V1
H1
V2
H2
V3
H3
V4
H4
V5
H5
"1" OEHOEVL
AT94K Family
10
Figure 5. Some Single Cell Modes
3 LUT3 LUT3 LUT3 LUT 4 LUT2:1 MUX 3 LUT3 LUT
DQ
DQ
Q
Q (Registered)
DQ
DQ
Synthesis Mode
Arithmetic Mode
DSP/Multiplier Mode
Counter Mode
Tri-State/Mux Mode
A
B
C
D
A
B
C
A
B
C
D
A
B
C
EN
Q
Q
SUM (Registered)
SUM
and/or
PRODUCT
or
CARRY
PRODUCT (Registered)
CARRY
CARRY
CARRY IN
and/or
or
and/or
and/or
AT94K Family
11
RAM
There are two types of RAM in the FPSLIC device. The FreeRAM distributed through the FPGA Core and the SRAM
shared by the AVR and FPGA. The SRAM is described in Section 2 FPGA/AVR Interface and System Controlon page
21. The 32 x 4 dual-ported FPGA FreeRAM blocks are dispersed throughout the array and are connected in each sector as
shown in Figure 6. A four-bit Input Data bus connects to four horizontal local buses (Plane 1) distributed over four sector
rows. A four-bit Output Data bus connects to four horizontal local buses (Plane 2) distributed over four sector rows. A five-
bit Input-address bus connects to five vertical express buses in same sector column (column 3). A five-bit Output-address
bus connects to five vertical express buses in same column. WAddr (Write Address) and RAddr (Read Address) alternate
positions in horizontally aligned RAM blocks. For the left-most RAM blocks, RAddr is on the left and WAddr is on the right.
For the right-most RAM blocks, WAddr is on the left and RAddr is tied off. For single-ported RAM, WAddr is the
READ/WRITE address port and Din is the (bi-directional) data port. Right-most RAM blocks can be used only for single-
ported memories. WE and OE connect to the vertical express buses in the same column on Plane V1 and V2, respectively.
WAddr, RAddr, WE and OE connect to express buses that are full length at array edge.
Reading and writing the 32 x 4 dual-port RAM are independent of each other. Reading the 32 x 4 dual-port RAM is com-
pletely asynchronous. Latches are transparent; when Load is logic 1, data flows through; when Load is logic 0, data is
latched. Each bit in the 32 x 4 dual-port RAM is also a transparent latch. The front-end latch and the memory latch together
form an edge-triggered flip-flop. When a Bit nibble is (Write) addressed and LOAD is logic 1 and WE is logic 0, DATA flows
through the bit. When a nibble is not (Write) addressed or LOAD is logic 0 or WE is logic 1, DATA is latched in the nibble.
The two CLOCK muxes are controlled together; they both select CLOCK or they both select 1. CLOCK is obtained from
the clock for the sector-column immediately to the left and immediately above the RAM block. Writing any value to the RAM
Clear Byte during configuration clears the RAM.
Figure 6. FPGA RAM Connections (One RAM Block)
32X4 RAM
Din
WAddr
WE
OE
Dout
RAddr
CLK
CLK
CLK
CLK
CLK
Sector Clock Mux
AT94K Family
12
Figure 7. FreeRAM Logic(1)
Note: 1. For dual port, the switches on READ ADDR and DATA OUT would be on. The other two would be off. The reverse is true for
single port.
Write
Data Data
Read
"1""1"
Write Enable
RAM-Clear
DATA OUT
"1"
CLOCK
Load
5
READ ADDR
WRITE ADDR
WE
DATA IN
Load
Latch
Load
Latch
Load
Latch
Clear
32 x 4
DUAL-PORT
RAM
OE
4
4
5
AT94K Family
13
Figure 8. FreeRAM Example: 128 x 8 Dual-ported RAM (Asynchronous)(1)
Note: 1. These layouts can be generated automatically using the Macro Generators.
2-to-4
Decoder
Dout(4)
Dout(5)
Dout(6)
Dout(7)
Din Dout
WE
OE
RAddr WAddr
Din Dout Din Dout
WE
OE
Din Dout
WAddr RAddr
WE
OE
RAddr WAddr
WE
OE
WAddr RAddr
Din Dout
WAddr RAddr
WE
OE
Din Dout
WE
OE
RAddr WAddr
Din Dout
WAddr RAddr
WE
OE
Din Dout
WE
OE
RAddr WAddr
2-to-4
Decoder
Local Buses
Express Buses
Dedicated Connections
Read
Address
Din(0)
Din(1)
Din(2)
Din(3)
Din(4)
Din(5)
Din(6)
Din(7)
Write
Address
WE
Dout(0)
Dout(1)
Dout(2)
Dout(3)
AT94K Family
14
Clocking and Set/Reset
Six of the eight dedicated Global Clock buses (1, 2, 3, 4, 7 and 8) are connected to a dual-use Global Clock pin. In addition,
two Global Clock buses (5 and 6) are driven from clock signals generated within the AVR microcontroller core (See
Figure 9).
An FPGA core internal signal can be placed on any Global Clock bus by routing that signal to a Global clock access point
in the corners of the embedded core. Each column of the array has a Column Clock selected from one of the eight Global
Clock buses. The extreme-left Column Clock mux has two additional inputs from dual-use pins FCK1 and FCK2 to provide
fast clocking to left-side I/O. Each sector column of four cells can be clocked from a (Plane 4) express bus or from the Col-
umn Clock. Clocking to the 4 cells of a sector can be disabled. The Plane 4 express bus used for clocking is half length at
the array edge. The clock provided to each sector column of four cells can be either inverted or not inverted. The register in
each cell is triggered on a rising clock edge. On power-up, constant 0 is provided to each registers clock pins. A dedi-
cated Global Set/Reset bus can be driven by any USER I/O pad, except those used for clocking, Global or Fast. An internal
signal can be placed on the Global Set/Reset bus by routing that signal to the pad programmed as the Global Set/Reset
input. Global Set/Reset is distributed to each column of the array. Each sector column of four cells can be Set/Reset by a
(Plane 5) express bus or by the Global Set/Reset. The Plane 5 express bus used for Set/Reset is half length at array edge.
The Set/Reset provided to each sector column of four cells can be either inverted or not inverted. The function of the
Set/Reset input of a register (either Set or Reset) is determined by a configuration bit for each cell. The Set/Reset input of
a register is Active Low (logic 0). Setting or resetting of a register is asynchronous. On power-up, a logic 1 (a high) is pro-
vided by each register, i.e., all registers are set at power-up.
Figure 9. FPGA Clocks from AVR
AVR SYSTEM CLOCK (AVR CLK)
TIMER OSC TOSC1 (AS2 SET IN ASSR)
AVR SYSTEM
CLOCK
(AVR CLK)
WATCHDOG CLOCK
"1"
GCK6
TO FPGA
CORE GCK5
TO FPGA
CORE GCK6
AT94K Family
15
The FPGA clocks from the AVR are effected differently in the various sleep modes in AVR sleep modes.
The source clock into the FPGA GCK5 and GCK6 will determine what happens during the various power-down modes of
the AVR.
If the XTAL clock input is used as an FPGA clock (GCK5 or GCK6) in Idle mode, it will still be running and in Power-
down/save, it will be off.
If the TOSC clock input is used as an FPGA clock (GCK6) in Idle mode, it will still be running in Power-save mode but will
be off in Power-down mode.
If the Watchdog Timer is used as an FPGA clock (GCK6) and was enabled in the AVR, it will be running in all sleep modes.
Table 2. Clock Activity in Various Modes
Mode Clock Source GCK5 GCK6
Idle
XTAL Active Active
TOSC Not Available Active
WDT Not Available Active
Power-save
XTAL Inactive Inactive
TOSC Not Available Active
WDT Not Available Active
Power-down
XTAL Inactive Inactive
TOSC Not Available Inactive
WDT Not Available Active
AT94K Family
16
Figure 10. Clocking (for one column of cells)
Global Clock Line (Buried)
Express Bus
(Plane 4; Half Length at Edge)
GCK1 - GCK8
Repeater
}
}
"1"
"1"
"1"
"1"
FCK (2 on Left Edge Column of Embedded FPGA Array Only)
AT94K Family
17
Figure 11. Set/Reset (for one column of cells)
Each Cell has a Programmable Set or Reset
Global Set/Reset Line (Buried)
Repeater
Express Bus
(Plane 5; Half Length at Edge)
Any User I/O can Drive Global Set/Reset Line
"1"
"1"
"1"
"1"
AT94K Family
18
Some of the bus resources on the embedded FPGA core are used as dual-function resources. Table 3 shows which buses
are used in a dual-function mode and which bus plane is used. The FPGA software tools are designed to automatically
accommodate dual-function buses in an efficient manner.
Figure 12. Primary I/O
Table 3. Dual-function Buses
Function Type Plane(s) Direction Comments
Cell Output Enable Local 5 Horizontal and
Vertical
FreeRAM Output Enable Express 2 Vertical Bus Full Length at Array Edge
Bus in First Column to Left of RAM Block
FreeRAM Write Enable Express 1 Vertical Bus Full Length at Array Edge
Bus in First Column to Left of RAM Block
FreeRAM Address Express 1 - 5 Vertical Buses Full Length at Array Edge
Buses in Second Column to Left of RAM Block
FreeRAM Data In Local 1 Horizontal
FreeRAM Data Out Local 2 Horizontal
Clocking Express 4 Vertical Bus Full Length at Array Edge
Set/Reset Express 5 Vertical Bus Full Length at Array Edge
"0"
"1"
DRIVE
TRI-STATE
"0"
"1"
TTL/ CMO S
SCHMITT
DELAY
PULL-DOWN
PULL-UP
GND VCC
PAD
CELL
CELL
CELL
ICLK
RST
RST
0CLK
AT94K Family
19
Figure 13. Secondary I/O
Figure 14. Primary and Secondary I/Os
CELL
"0"
"1"
DRIVE
TRI-STATE
"0"
"1"
TTL/CMOS
SCHMITT
DELAY
PULL-DOWN
PULL-UP
GND VCC
PAD
CELL
ICLK
RST
RST
ICLK
cell cell
cell cell
cell cell
cell cell
cell cell
cell cell
pp
pp
pp
p
p
p
p
p
p
ss s
s
s
ss
s
p
s
AT94K Family
20
Figure 15. Corner I/Os
DRIVE
TRI-STATE
TTL/CMOS
SCHMITT
DELAY
PULL-DOWN
PULL-UP
GNDVCC
PAD
DRIVE
TRI-STATE
TTL/CMOS
SCHMITT
DELAY
PULL-DOWN
PULL-UP
GNDVCC
PAD
"0"
"1"
"0"
"1"
"0"
"1"
"0"
"1"
DRIVE
TRI-STATE
TTL/ CMO S
SCHMITT
DELAY
PULL-DOWN
PULL-UP
GND VCC
PAD
"0"
"1"
"0"
"1"
CELL
CELL
CELL
CELL
CLK
RST
CLK
RST
CLK
RST
CLK
RST
CLK
RST
CLK
RST
AT94K Family
21
Section 2 FPGA/AVR Interface and System Control
The FPGA and AVR share a flexible interface which allows for many methods of system integration.
Both FPGA and AVR share access to the 15 ns dual-port SRAM.
The AVR data bus interfaces directly into the FPGA busing resources, effectively treating the FPGA as a large I/O
device. Users have complete flexibility on the types of additional peripherals which are placed and routed inside the
FPGA user logic. Up to 16 decoded address lines are provided into the FPGA.
Up to 16 interrupts are available from the FPGA to the AVR.
The AVR can reprogram the FPGA during operation to create a dynamic reconfigurable system (Cache Logic).
FPGA/AVR Interface Memory-mapped Peripherals
The FPGA core can be directly accessed by the AVR core (as shown in Figure 16). Four memory locations in the AVR
memory map are decoded into 16 select lines (8 for AT94K05) and are presented to the FPGA along with the AVR 8-bit
data bus. The FPGA can be used to create additional custom peripherals for the AVR microcontroller through this interface.
In addition there are 16 interrupt lines (8 for AT94K05) from the FPGA back into the AVR interrupt controller. Programma-
ble peripherals or regular logic can use these interrupt lines. Full support for programmable peripherals is available within
the System Designer tool suite.
Figure 16. FPGA/AVR Interface: Interrupts and Addressing
The FPGA I/O selection is controlled by the AVR. This is described in detail beginning on page 53. The FPGA I/O interrupts
are described beginning on page 56.
EMBEDDED
FPGA CORE
EMBEDDED
AVR CORE
ADDRESS
DECODER
4:16
DECODE
Up to 16 Memory-mapped
Decoded Address
Lines from 4 I/O Memory
Space Addresses I/O Memory Address Bus
FPGAIORE
FPGAIOWE
Up to 16 Interrupt Lines from FPGA to AVR Various Priority Levels
8-bit Bidirectional Data Bus
8-bit
Data Out
8-bit
Data In
AT94K Family
22
Program and Data SRAM
Between the FPGA and the AVR resides up to 36 Kbytes of 15 ns dual-port SRAM. This SRAM is used by the AVR for pro-
gram instruction and general-purpose data storage. The AVR is connected to one side of this SRAM; the FPGA is
connected to the other side. The port connected to the FPGA is used to store data without using up bandwidth on the AVR
system data bus.
The FPGA core communicates directly with the data SRAM block, viewing all SRAM memory space as 8-bit memory.
For the AT94K10 and AT94K40, the internal program and data SRAM is divided into three blocks: 10 Kbytes x 16 dedi-
cated program SRAM, 4 Kbytes x 8 dedicated data SRAM and 6 Kbytes x 16 or 12 Kbytes x 8 configurable SRAM, which
may be swapped between program and data memory spaces in 2 Kbytes x 16 or 4 Kbytes 8 partitions.
For the AT94K05, the internal program and data SRAM is divided into three blocks: 4 Kbytes 16 dedicated program SRAM,
4 Kbytes x 8 dedicated data SRAM and 6 Kbytes x 16 or 12 Kbytes x 8 configurable SRAM, which may be swapped
between program and data memory spaces in 2 Kbytes x 16 or 4 Kbytes x 8 partitions.
The addressing scheme for the configurable SRAM partitions prevents program instructions from overwriting data words
and vice versa. Once configured (SCR41:40 see System Control Register on page 32), the program memory space
remains isolated from the data memory space. SCR41:40 controls internal muxes and write enable signals allow the mem-
ory to be safely segmented.
AT94K Family
23
Figure 17. FPSLIC Configurable Allocation SRAM Memory(1)(2)
Notes: 1. The Soft BOOT BLOCK is an area of memory that is first loaded when the part is powered up and configured. The remain-
der of the memory can be reprogrammed while the device is in operation for switching functions in and out of memory. The
Soft BOOT BLOCK can only be programmed by a full device configuration on power-up.
2. The lower portion of the Data memory is not shared between the AVR and FPGA. The AVR uses addresses $0000 - $001F
for the AVR CPU general working registers. $001F - $005F are the addresses used for Memory Mapped I/O and store the
information in dedicated registers. Therefore, on the FPGA side $0000 - $005F are available for data that is only needed by
the FPGA.
$0000
$07FF
$27FF
$3FFF
$3800
$3000
$37FF
$2800
$2FFF
$0FFF
$1000
$1FFF
$2000
$2FFF
$3000
$3FFF
$005F
Memory Partition
is User Defined
during Development FIXED
10K x 16
4 Kbytes x 16 (94K05)
OPTIONAL
2 Kbytes x 16
OPTIONAL
2 Kbytes x 16
OPTIONAL
2 Kbytes x 16
OPTIONAL
4 Kbytes x 8
OPTIONAL
4 Kbytes x 8
OPTIONAL
4 Kbytes x 8
Program SRAM Memory
Data SRAM Memory
B SIDE A SIDE
FIXED
4 Kbytes x 8
$0000
DATA
SRAM
FPGA
ACCESS
ONLY
$001F
AVR REG.
SPACE
SOFT BOOT BLOCK
AVR
MEMORY
MAPPED
I/O
(1)
(2)
AT94K Family
24
Data SRAM Access by FPGA FPGAFrame Mode
The FPGA user logic has access to the data SRAM directly through the FPGA side of the dual-port memory. A single bit in
the configuration control register (SCR63 see System Control Register on page 32) enables this interface. The interface
is disabled during configuration downloads. Express buses on the East edge of the array are used to interface the memory.
Full read and write access is available. To allow easy implementation, the interface itself is dedicated in routing resources,
and is controlled in the System Designer software suite using the AVR FPGA interface dialog.
Figure 18. Internal SRAM Access Normal Use
Once the SCR63 bit is set there is no additional read enable from the FPGA side. This means that the read is always
enabled. You can also perform a read or write from the AVR at the same time as an FPGA read or write. If there is a possi-
bility of a write address being accessed by both devices, at the same time, the designer should add arbitration to the FPGA
Logic to control who has priority. In most cases the AVR would be used to restrict access by the FPGA using the FMXOR
bit see Software Control Register SFTCRon page 51. You can read from the same location from both sides
simultaneously.
SCR bit 38 controls the polarity of the clock to the SRAM from the AT40K FPGA.
SRAM Access by FPGA/AVR to Allow for Code (Program Memory) Changes
Accessing and Modifying the Program Memory from the AVR
The FPSLIC SRAM is up to 36 Kbytes x 8 of dual port (see Figure 17):
The A side (port) is accessed by the AVR.
The B side (port) is accessed by the FPGA/Configuration Logic.
The B side (port) can be accessed by the AVR with ST and LD instructions in DBG mode for code self-modify.
Structurally, the [(n 2) Kbytes 8] memory is built from (n)2 Kbytes 8 blocks, numbered SRAM0 through SRAM(n).
A Side
The A side is partitioned into program memory and data memory:
Program memory is 16-bit words.
Program memory address $0000 always starts in the highest two SRAMs (n - 1, n) [SRAMn - 1 (low byte) and SRAMn
(high byte)] (SRAM labels are for layout, the addressing scheme is transparent to the AVR PC).
EMBEDDED
FPGA CORE
EMBEDDED
AVR CORE
DATA SRAM
4 Kbytes x 8
UP TO
16 Kbytes x 8
16 Address Lines:
FPGA Edge Express Buses 16-bit Data Address Bus
CLK AVR
WE AVR
RE AVR
8-bit Data Write
8-bit Data Read/Write
CLK FPGA
WE FPGA
8-bit Data Read
SCR38
AT94K Family
25
System configuration determines the higher addresses for program memory:
SCR bits 41 = 0 : 40 = 0, program memory extended from $2800 - $3FFF
SCR bits 41 = 0 : 40 = 1, program memory extended from $2800 - $37FF
SCR bits 41 = 1 : 40 = 0, program memory extended from $2800 - $2FFF
SCR bits 41 = 1 : 40 = 1, no extra program memory
Extended program memory is always lost to extended data memory from SRAM2/3 down to SRAM6/7.
Data memory is 8-bit words.
Data memory address $0000 always starts in SRAM0 (SRAM labels are for layout, the addressing scheme is
transparent to AVR data read/write).
System configuration determines the higher address for data memory:
SCR bits 41 = 0 : 40 = 0, no extra data memory
SCR bits 41 = 0 : 40 = 1, data memory extended from $1000 - $1FFF
SCR bits 41 = 1 : 40 = 0, data memory extended from $1000 - $2FFF
SCR bits 41 = 1 : 40 = 1, data memory extended from $1000 - $3FFF
Extended data memory is always lost to extended program memory from SRAM7 up to SRAM2 in 2 x SRAM blocks.
Table 4. AVR Program Decode for SRAM 2:7 (16K16)
Address Range SRAM Comments
$3FFF - $3800
$3FFF - $3800
02
03 CR41:40 = 00
$37FF - $3000
$37FF - $3000
04
05 CR41:40 = 00,01
$2FFF - $2800
$2FFF - $2800
06
07 CR41:40 = 00,01,10
$27FF - $2000
$27FF - $2000
$1FFF - $1800
$1FFF - $1800
$17FF - $1000
$17FF - $1000
$0FFF - $0800
$0FFF - $0800
$07FF - $0000
$07FF - $0000
08
09
10
11
12
13
14
15
16
n = 17
AVR Program Read-only
AVR Program Read-only
AVR Program Read-only
AVR Program Read-only
AVR Program Read-only
AVR Program Read-only
AVR Program Read-only
AVR Program Read-only
AVR Program Read-only
AVR Program Read-only
Table 5. AVR Data Decode for SRAM 0:17 (16K8)
Address Range SRAM Comments
$07FF - $0000
$0FFF - $0800
00
01
AVR Data Read/Write
AVR Data Read/Write
$17FF - $1000
$1FFF - $1800
02
03 CR41:40 = 11,10,01
$27FF - $2000
$2FFF - $2800
04
05 CR41:40 = 11,10
$37FF - $3000
$3FFF - $3800
06
07 CR41:40 = 11
AT94K Family
26
B Side
The B side is not partitioned; the FPGA (and AVR debug mode) views the memory space as 36 Kbytes 8.
The B side is accessed by the FPGA/Configuration Logic.
The B side is accessed by the AVR with ST and LD instructions in DBG mode for code self-modify.
To activate the debug mode and allow the AVR to access the program code space (with ST and LD instructions), the
DBG bit (bit 1) of the SFTCR $3A ($5A) register has to be set. When this bit is set, SCR36 and SCR37 are ignored
you can overwrite anything in the AVR program memory.
The FPGA memory access interface should be disabled while in debug mode. This is to ensure that there is no conten-
tion between the FPGA address and data signals and the AVR-generated address and data signals. To ensure the
AVR has control over the B side memory interface, the FMXOR bit (bit 3) of the SFTCR $3A ($5A) register should be
used in conjunction with the SCR63 system control register bit.
The FMXOR bit is XORed with the System Control Registers Enable FPGA SRAM Interface bit (SCR63). The behavior
when this bit is set to 1 is dependent on how the SCR was initialized. If the Enable FPGA SRAM Interface bit (SCR63)
in the SCR is 0, the FMXOR bit enables the FPGA SRAM Interface when set to 1. If the Enable FPGA SRAM Interface
bit in the SCR is 1, the FMXOR bit disables the FPGA SRAM Interface when set to 1. During AVR reset, the FMXOR bit
is cleared by hardware.
Even though the FPGA (and AVR debug mode) views the memory space as 36 Kbytes 8, an awareness of the 2K x 8
partitions (or SRAM labels) is required if Frame (and AVR debug mode) read/writes are to be meaningful to the AVR.
AVR data to FPGA addressing is 1:1 mapping.
AVR program to FPGA addressing requires 16-bit to 8-bit mapping and an understanding of the partitions in the table
below.
Note: 1. Whether these SRAMs are data or program depends on SCR40 and SCR41 values.
Table 6. Summary Table for AVR and FPGA SRAM Addressing
SRAM
FPGA and AVR DBG
Address Range AVR Data Address Range AVR PC Address Range
00 $0000 - $07FF $0000 - $07FF
01 $0800 - $0FFF $0800 - $0FFF
02(1) $1000 - $17FF $1000 - $17FF $3800 - $3FFF (LS byte)
03(1) $1800 - $1FFF $1800 - $1FFF $3800 - $3FFF (MS byte)
04(1) $2000 - $27FF $2000 - $27FF $3000 - $37FF (LS byte)
05(1) $2800 - $2FFF $2800 - $2FFF $3000 - $37FF (MS byte)
06(1) $3000 - $37FF $3000 - $37FF $2800 - $2FFF (LS byte)
07(1) $3800 - $3FFF $3800 - $3FFF $2800 - $2FFF (MS byte)
08 $4000 - $47FF $2000 - $27FF (LS byte)
09 $4800 - $4FFF $2000 - $27FF (MS byte)
10 $5000 - $57FF $1800 - $1FFF (LS byte)
11 $5800 - $5FFF $1800 - $1FFF (MS byte)
12 $6000 - $67FF $1000 - $17FF (LS byte)
13 $6800 - $6FFF $1000 - $17FF (MS byte)
14 $7000 - $77FF $0800 - $0FFF (LS byte)
15 $7800 - $7FFF $0800 - $0FFF (MS byte)
16 $8000 - $87FF $0000 - $07FF (LS byte)
17 = n $8800 - $8FFF $0000 - $07FF (MS byte)
AT94K Family
27
Example: Frame (and AVR debug mode) write of instructions to associated AVR PC addresses:
Table 7. AVR PC Addresses
AVR PC Instruction
0ffe 9b28
0fff cffe
1000 b300
1001 9a39
Table 8. Frame Addresses
Frame Address Frame Data
77fe 28
77ff fe
6000 00
6001 39
7ffe 9b
7fff cf
6800 b3
6801 9a
AT94K Family
28
Figure 19. AVR SRAM Data Memory Write Using ST Instruction
Figure 20. AVR SRAM Data Memory Read Using LD Instruction
CLOCK
RAMWE
RAMADR
DBUS
DBUSOUT
(REGISTERED)
VALID
ST cycle 1 ST cycle 2 next instruction
VALID
VALID
CLOCK
RAMRE
RAMADR
DBUS
VALID
LD cycle 1 LD cycle 2 next instruction
VALID
AT94K Family
29
AVR Cache Mode
The AVR has the ability to cache download the FPGA memory. The AVR has direct access to the data buses of the
FPGAs configuration SRAM and is able to download bitstreams. AVR Cache access of configuration SRAM is not avail-
able during normal configuration downloads. The Cache Logic port in the AVR is located in the I/O memory map. Three
registers, FPGAX, FPGAY FPGAZ, control the address written to inside the FPGA; and FPGAD in the AVR memory map
controls the Data. Registers FPGAX, FPGAY and FPGAZ are write only.
The AVR Cache Logic access mode is write only. Transfers may be aborted at any time due to AVR program wishes or
external interrupts.
The FPGA CHECK function is not supported by the AVR Cache mode.
A typical application for this mode is for the AVR to accept serial data through a UART for example, and port it as configu-
ration data to the FPGA, thereby affecting a download, or allowing reconfigurable systems where the FPGA is updated
algorithmically by AVR. Please refer to FPSLIC Configuration datasheet for more details.
See page 52 FPGA Cache Logic for more details.
Figure 21. Internal FPGA Configuration Access
EMBEDDED
FPGA CORE
(Operation is not
interrupted during
Cache Logic
Loading)
EMBEDDED
AVR CORE
32-BIT CONFIGURATION WORD
Configuration Logic
FPGAD [7:0]
8-bit Configuration
Memory Write Data
24-bit Address Write
FPGAX [7:0]
FPGAY [7:0]
FPGAZ [7:0]
Configuration Clock Each tick is generated when the Memory-
mapped I/O location FPGAD is written to inside the AVR.
MEMORY-MAPPED
LOCATION
MEMORY-MAPPED
LOCATION
MEMORY-MAPPED
LOCATION
MEMORY-MAPPED
LOCATION
CACHEIOWE
AT94K Family
30
Resets
The user must have the flexibility to issue resets and reconfiguration commands to separate portions of the device. There
are two Reset pins on the FPSLIC device. The first, RESET, results in a clearing of all FPGA configuration SRAM and the
System Control Register, and initiates a download if in mode 0. The AVR will stop and be reset.
A second reset pin, AVRReset, is implemented to reset the AVR portion of the FPSLIC functional blocks. This is described
in the Reset Sourceson page 59.
System Control
Configuration Modes
The AT94K family has four configuration modes controlled by mode pins M0 and M2. The following table shows the modes
of operation:
Modes 2 and 3 are reserved and are used for factory test.
Modes 0 and 1 are pin-compatible with the appropriate AT40K counterpart. AVR I/O will be taken over by the configuration
logic for the CHECK pin during both modes.
See the AT94K Series Configuration document for details on downloading bitstreams.
System Control Register FPGA/AVR
The configuration control register in the FPSLIC consists of 8 bytes of data, which are loaded with the FPGA/Prog. Code at
power-up from external nonvolatile memory. FPSLIC System Control Register values can be set in the System Designer
software. Recommended defaults are included in the software.
Table 9. Configuration Modes
M2 M0 Name
0 0 Mode 0 - Master Serial
0 1 Mode 1 - Slave Serial Cascade
1 0 Mode 2 - Reserved
1 1 Mode 3 - Reserved
Bit Description
SCR0 - SCR1 Reserved
SCR2 0 = Enable Cascading
1 = Disable Cascading
SCR2 controls the operation of the dual-function I/O CSOUT. When SCR2 is set, the CSOUT pin is not used by
the configuration during downloads, set this bit for configurations where two or more devices are cascaded
together. This applies for configuration to another FPSLIC device or to an FPGA.
SCR3 0 = Check Function Enabled
1 = Check Function Disabled
SCR3 controls the operation of the CHECK pin and enables the Check Function. When SCR3 is set, the dual
use AVR I/O/CHECK pin is not used by the configuration during downloads, and can be used as AVR I/O.
SCR4 0 = Memory Lockout Disabled
1 = Memory Lockout Enabled
SCR4 is the Security Flag and controls the writing and checking of configuration memory during any
subsequent configuration download. When SCR4 is set, any subsequent configuration download initiated by
the user, whether a normal download or a CHECK function download, causes the INIT pin to immediately
activate. CON is released, and no further configuration activity takes place. The download sequence during
which SCR4 is set is NOT affected. The Control Register write is also prohibited, so bit SCR4 may only be
cleared by a power-on reset or manual reset.
SCR5 Reserved
AT94K Family
31
SCR6 0 = OTS Disabled
1 = OTS Enabled
Setting SCR6 makes the OTS (output tri-state) pin an input which controls the global tri-state control for all user
I/O. This junction allows the user at any time to tristate all user I/O and isolate the chip.
SCR7 - SCR12 Reserved
SCR13 0 = CCLK Normal Operation
1 = CCLK Continues After Configuration.
Setting bit SCR13 allows the CCLK pin to continue to run after configuration download is completed. This bit is
valid for Master mode, mode 0 only. The CCLK is not available internally on the device. If it is required in the
design, it must be connected to another device I/O.
SCR14 - SCR15 Reserved
SCR16 - SCR23 0 = GCK 0:7 Always Enabled
1 = GCK 0:7 Disabled During (Internal and External) Configuration Download.
Setting SCR16:SCR23 allows the user to disable the input buffers driving the global clocks. The clock buffers
are enabled and disabled synchronously with the rising edge of the respective GCK signal, and stop in a high
1 state. Setting one of these bits disables the appropriate GCK input buffer only and has no effect on the
connection from the input buffer to the FPGA array.
SCR24 - SCR25 0 = FCK 0:1 Always Enabled
1 = FCK 0:1 Disabled During (Internal and External) Configuration Download.
Setting SCR24:SCR25 allows the user to disable the input buffers driving the fast clocks. The clock buffers are
enabled and disabled synchronously with the rising edge of the respective FCK signal, and stop in a high 1
state. Setting one of these bits disables the appropriate FCK input buffer only and has no effect on the
connection from the input buffer to the FPGA array.
SCR26 - SCR29 Reserved
SCR30 0 = Global Set/Reset Normal
1 = Global Set/Reset Active (Low) During (Internal and External) Configuration Download.
SCR30 allows the Global set/reset to hold the core DFFs in reset during any configuration download. The
Global set/reset net is released at the end of configuration download on the rising edge of CON, if set.
SCR31 0 = Disable I/O Tri-state
1 = I/O Tri-state During (Internal and External) Configuration Download.
SCR31 forces all user defined I/O pins to go tri-state during configuration download. Tri-state is released at the
end of configuration download on the rising edge of CON, if set.
SCR32 - SCR34 Reserved
SCR35 0 = AVR Reset Pin Disabled
1 = AVR Reset Pin Enabled
SCR35 allows the AVR Reset pin to reset the AVR only.
SCR36 0 = Protect AVR Program SRAM
1 = Allow Writes to AVR Program SRAM (Excluding Boot Block)
SCR36 protects AVR program code from writes by the FPGA Data SRAM writes.
SCR37 0 = AVR Program SRAM Boot Block Protect
1 = AVR Program SRAM Boot Block Allows Overwrite
SCR38 0 = (default) Frame Clock Inverted to AVR Data/Program SRAM
1 = Non-inverting Clock Into AVR Data/Program SRAM
SCR39 Reserved
Bit Description
AT94K Family
32
SCR40 - SCR41 00 = 16 Kbytes x 16 Program/4 Kbytes x 8 Data
01 = 12 Kbytes x 16 Program/12 Kbytes x 8 Data
10 = 14 Kbytes x 16 Program/8 Kbytes x 8 Data
11 = 10 Kbytes x 16 Program/16 Kbytes x 8 Data
SCR40 : SCR41 AVR program/data SRAM partitioning (set by using the AT94K Device Options in System
Designer).
SCR 42 - SCR47 Reserved
SCR48 0 = EXT-INT0 Driven By Port E<4>
1 = EXT-INT0 Driven By INTP0 pad
SCR48 : SCR53 Defaults dependent on package selected.
SCR49 0 = EXT-INT1 Driven By Port E<5>
1 = EXT-INT1 Driven By INTP1 pad
SCR48 : SCR53 Defaults dependent on package selected.
SCR50 0 = EXT-INT2 Driven By Port E<6>
1 = EXT-INT2 Driven By INTP2 pad
SCR48 : SCR53 Defaults dependent on package selected.
SCR51 0 = EXT-INT3 Driven By Port E<7>
1 = EXT-INT3 Driven By INTP3 pad
SCR48 : SCR53 Defaults dependent on package selected.
SCR52 0 = UART0 Pins Assigned to Port E<1:0>
1 = UART0 Pins Assigned to UART0 pads
SCR48 : SCR53 Defaults dependent on package selected.
SCR53 0 = UART1 Pins Assigned to Port E<3:2>
1 = UART1 Pins Assigned to UART1 pads
SCR48 : SCR53 Defaults dependent on package selected.
On packages less than 144-pins, there is reduced access to AVR ports. Port D is not available externally in the
smallest package and Port E becomes dual-purpose I/O to maintain access to the UARTs and external
interrupt pins. The Pin List (East Side) on page 154 shows exactly which pins are available in each package.
SCR54 0 = AVR Port D I/O With 6 mA Drive
1 = AVR Port D I/O With 20 mA Drive
SCR55 0 = AVR Port E I/O With 6 mA Drive
1 = AVR Port E I/O With 20 mA Drive
SCR56 0 = Disable XTAL Pin (Rfeedback)
1 = Enable XTAL2 Pin (Rfeedback)
SCR57 0 = Disable TOSC2 Pin (Rfeedback)
1 = Enable TOSC2 Pin (Rfeedback)
SCR58 - SCR59 Reserved
SCR60 - SCR61 00 = 1
01 = Timer Oscillator Clock (TOSC1)(1)
10 = AVR System Clock
11 = Watchdog Clock
Global Clock 6 mux select (set by using the AT94K Device Options in System Designer).
Note: 1. The AS2 bit must be set in the ASSR register.
SCR62 0 = Disable Cache Logic Writes to FPGA by AVR
1 = Enable Cache Logic Writes to FPGA by AVR
SCR63 0 = Disable Access (Read and Write) to SRAM by FPGA
1 = Enable Access (Read and Write) to SRAM by FPGA
Bit Description
AT94K Family
33
Section 3 AVR Core and Peripherals
AVR Core
Watchdog Timer/On-chip Oscillator
Oscillator-to-Internal Clock Circuit
Oscillator-to-Timer/Counter for Real-time Clock
16-bit Timer/Counter and Two 8-bit Timer/Counters
Interrupt Unit
Multiplier
UART (0)
UART (1)
I/O Port D (full 8 bits available on 144-pin or higher devices)
I/O Port E
The embedded AVR core is a low-power CMOS 8-bit microcontroller based on the AVR RISC architecture. By executing
powerful instructions in a single-clock-cycle, the embedded AVR core achieves throughputs approaching 1 MIPS per MHz
allowing the system architect to optimize power consumption versus processing speed.
The AVR core is based on an enhanced RISC architecture that combines a rich instruction set with 32 x 8 general-
purpose working registers. All the 32 x 8 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing two
independent register bytes to be accessed in one single instruction executed in one clock cycle. The resulting
architecture is more code efficient while achieving throughputs up to ten times faster than conventional CISC
microcontrollers.
The embedded AVR core provides the following features: 16 general-purpose I/O lines, 32 x 8 general-purpose working
registers, Real-time Counter (RTC), 3 flexible timer/counters with compare modes and PWM, 2 UARTs, programmable
Watchdog Timer with internal oscillator, 2-wire serial port and three software-selectable Power-saving modes. The Idle
mode stops the CPU while allowing the SRAM, timer/counters, two-wire serial port and interrupt system to continue func-
tioning. The Power-down mode saves the register contents but freezes the oscillator, disabling all other chip functions until
the next interrupt or hardware reset. In Power-save mode, the timer oscillator continues to run, allowing the user to main-
tain a timer base while the rest of the device is sleeping.
The embedded AVR core is supported with a full suite of program and system development tools including: C compilers,
macro assemblers, program debugger/simulators and evaluation kits.
Instruction Set Nomenclature (Summary)
Full instruction details available in the AVR Instruction Set document.
Status Register (SREG)
SREG: Status register
C: Carry flag in status register
Z: Zero flag in status register
N: Negative flag in status register
V: Twos complement overflow indicator
S: N V, For signed tests
H: Half-carry flag in the status register
T: Transfer bit used by BLD and BST instructions
I: Global interrupt enable/disable flag
AT94K Family
34
Registers and Operands
Rd: Destination (and source) register in the register file
Rr: Source register in the register file
R: Result after instruction is executed
K: Constant data
k: Constant address
b: Bit in the register file or I/O register (0 b 7)
s: Bit in the status register (0 s 2)
X,Y,Z: Indirect address register (X=R27:R26, Y=R29:R28 and Z=R31:R30)
A: I/O location address
q: Displacement for direct addressing (0 q 63)
I/O Registers
Stack
STACK: Stack for return address and pushed registers
SP: Stack Pointer to STACK
Flags
: Flag affected by instruction
0: Flag cleared by instruction
1: Flag set by instruction
-: Flag not affected by instruction
The instructions EIJMP, EICALL, ELPM, GPM, ESPM (from megaAVR Instruction Set) are not supported in the FPSLIC
device.
AT94K Family
35
Conditional Branch Summary
Complete Instruction Set Summary
Test Boolean Mnemonic Complementary Boolean Mnemonic Comment
Rd > Rr Z(N V) = 0 BRLT Rd Rr Z+(N V) = 1 BRGE Signed
Rd Rr (N V) = 0 BRGE Rd < Rr (N V) = 1 BRLT Signed
Rd = Rr Z = 1 BREQ Rd Rr Z = 0 BRNE Signed
Rd Rr Z+(N V) = 1 BRGE Rd > Rr Z(N V) = 0 BRLT Signed
Rd < Rr (N V) = 1 BRLT Rd Rr (N V) = 0 BRGE Signed
Rd > Rr C + Z = 0 BRLO Rd Rr C + Z = 1 BRSH Unsigned
Rd Rr C = 0 BRSH/BRCC Rd < Rr C = 1 BRLO/BRCS Unsigned
Rd = Rr Z = 1 BREQ Rd Rr Z = 0 BRNE Unsigned
Rd Rr C + Z = 1 BRSH Rd > Rr C + Z = 0 BRLO Unsigned
Rd < Rr C = 1 BRLO/BRCS Rd Rr C = 0 BRSH/BRCC Unsigned
Carry C = 1 BRCS No Carry C = 0 BRCC Simple
Negative N = 1 BRMI Positive N = 0 BRPL Simple
Overflow V = 1 BRVS No Overflow V = 0 BRVC Simple
Zero Z = 1 BREQ Not Zero Z = 0 BRNE Simple
Instruction Set Summary
Mnemonics Operands Description Operation Flags #Clock
Arithmetic and Logic Instructions
ADD Rd, Rr Add Without Carry Rd Rd + Rr Z,C,N,V,S,H 1
ADC Rd, Rr Add With Carry Rd Rd + Rr + C Z,C,N,V,S,H 1
ADIW Rd, K Add Immediate to Word Rd+1:Rd Rd+1:Rd + K Z,C,N,V,S 2
SUB Rd, Rr Subtract Without Carry Rd Rd - Rr Z,C,N,V,S,H 1
SUBI Rd, K Subtract Immediate Rd Rd - K Z,C,N,V,S,H 1
SBC Rd, Rr Subtract With Carry Rd Rd - Rr - C Z,C,N,V,S,H 1
SBCI Rd, K Subtract Immediate With Carry Rd Rd - K - C Z,C,N,V,S,H 1
SBIW Rd, K Subtract Immediate from Word Rd+1:Rd Rd+1:Rd - K Z,C,N,V,S 2
AND Rd, Rr Logical AND Rd Rd Rr Z,N,V,S 1
ANDI Rd, K Logical AND With Immediate Rd Rd K Z,N,V,S 1
OR Rd, Rr Logical OR Rd Rd v Rr Z,N,V,S 1
ORI Rd, K Logical OR With Immediate Rd Rd v K Z,N,V,S 1
EOR Rd, Rr Exclusive OR Rd Rd Rr Z,N,V,S 1
COM Rd Ones Complement Rd $FF - Rd Z,C,N,V,S 1
NEG Rd Twos Complement Rd $00 - Rd Z,C,N,V,S,H 1
SBR Rd, K Set Bit(s) in Register Rd Rd v K Z,N,V,S 1
CBR Rd, K Clear Bit(s) in Register Rd Rd ($FFh - K) Z,N,V,S 1
AT94K Family
36
INC Rd Increment Rd Rd + 1 Z,N,V,S 1
DEC Rd Decrement Rd Rd - 1 Z,N,V,S 1
TST Rd Test for Zero or Minus Rd Rd Rd Z,N,V,S 1
CLR Rd Clear Register Rd Rd Rd Z,N,V,S 1
SER Rd Set Register Rd $FF None 1
MUL Rd, Rr Multiply Unsigned R1:R0 Rd × Rr (UU) Z,C 2
MULS Rd, Rr Multiply Signed R1:R0 Rd × Rr (SS) Z,C 2
MULSU Rd, Rr Multiply Signed With Unsigned R1:R0 Rd × Rr (SU) Z,C 2
FMUL Rd, Rr Fractional Multiply Unsigned R1:R0 (Rd × Rr)<<1 (UU) Z,C 2
FMULS Rd, Rr Fractional Multiply Signed R1:R0 (Rd × Rr)<<1 (SS) Z,C 2
FMULSU Rd, Rr Fractional Multiply Signed With
Unsigned
R1:R0 (Rd × Rr)<<1 (SU) Z,C 2
Branch Instructions
RJMP k Relative Jump PC PC + k + 1 None 2
IJMP Indirect Jump to (Z) PC(15:0) ZNone2
JMP k Jump PC k None 3
RCALL k Relative Call Subroutine PC PC + k + 1 None 3
ICALL Indirect Call to (Z) PC(15:0) ZNone3
CALL k Call Subroutine PC kNone4
RET Subroutine Return PC STACK None 4
RETI Interrupt Return PC STACK I 4
CPSE Rd, Rr Compare, Skip if Equal if (Rd = Rr) PC PC + 2 or 3 None 1 / 2 / 3
CP Rd, Rr Compare Rd - Rr Z,C,N,V,S,H 1
CPC Rd, Rr Compare With Carry Rd - Rr - C Z,C,N,V,S,H 1
CPI Rd, K Compare With Immediate Rd - K Z,C,N,V,S,H 1
SBRC Rr, b Skip if Bit in Register Cleared if (Rr(b) = 0) PC PC + 2 or 3 None 1 / 2 / 3
SBRS Rr, b Skip if Bit in Register Set if (Rr(b) = 1) PC PC + 2 or 3 None 1 / 2 / 3
SBIC A, b Skip if Bit in I/O Register Cleared if(I/O(A,b) = 0) PC PC + 2 or 3 None 1 / 2 / 3
SBIS A, b Skip if Bit in I/O Register Set If(I/O(A,b) = 1) PC PC + 2 or 3 None 1 / 2 / 3
BRBS s, k Branch if Status Flag Set if (SREG(s) = 1) then PC PC+k+1 None 1 / 2
BRBC s, k Branch if Status Flag Cleared if (SREG(s) = 0) then PC PC+k+1 None 1 / 2
BREQ k Branch if Equal if (Z = 1) then PC PC + k + 1 None 1 / 2
BRNE k Branch if Not Equal if (Z = 0) then PC PC + k + 1 None 1 / 2
BRCS k Branch if Carry Set if (C = 1) then PC PC + k + 1 None 1 / 2
BRCC k Branch if Carry Cleared if (C = 0) then PC PC + k + 1 None 1 / 2
BRSH k Branch if Same or Higher if (C = 0) then PC PC + k + 1 None 1 / 2
Instruction Set Summary (Continued)
Mnemonics Operands Description Operation Flags #Clock
AT94K Family
37
BRLO k Branch if Lower if (C = 1) then PC PC + k + 1 None 1 / 2
BRMI k Branch if Minus if (N = 1) then PC PC + k + 1 None 1 / 2
BRPL k Branch if Plus if (N = 0) then PC PC + k + 1 None 1 / 2
BRGE k Branch if Greater or Equal, Signed if (N V= 0) then PC PC + k + 1 None 1 / 2
BRLT k Branch if Less Than, Signed if (N V= 1) then PC PC + k + 1 None 1 / 2
BRHS k Branch if Half-carry Flag Set if (H = 1) then PC PC + k + 1 None 1 / 2
BRHC k Branch if Half-carry Flag Cleared if (H = 0) then PC PC + k + 1 None 1 / 2
BRTS k Branch if T Flag Set if (T = 1) then PC PC + k + 1 None 1 / 2
BRTC k Branch if T Flag Cleared if (T = 0) then PC PC + k + 1 None 1 / 2
BRVS k Branch if Overflow Flag is Set if (V = 1) then PC PC + k + 1 None 1 / 2
BRVC k Branch if Overflow Flag is Cleared if (V = 0) then PC PC + k + 1 None 1 / 2
BRIE k Branch if Interrupt Enabled if (I = 1) then PC PC + k + 1 None 1 / 2
BRID k Branch if Interrupt Disabled if (I = 0) then PC PC + k + 1 None 1 / 2
Data Transfer Instructions
MOV Rd, Rr Copy Register Rd Rr None 1
MOVW Rd, Rr Copy Register Pair Rd+1:Rd Rr+1:Rr None 1
LDI Rd, K Load Immediate Rd KNone1
LDS Rd, k Load Direct from Data Space Rd (k) None 2
LD Rd, X Load Indirect Rd (X) None 2
LD Rd, X+ Load Indirect and Post-Increment Rd (X), X X + 1 None 2
LD Rd, -X Load Indirect and Pre-Decrement X X - 1, Rd (X) None 2
LD Rd, Y Load Indirect Rd (Y) None 2
LD Rd, Y+ Load Indirect and Post-Increment Rd (Y), Y Y + 1 None 2
LD Rd, -Y Load Indirect and Pre-Decrement Y Y - 1, Rd (Y) None 2
LDD Rd, Y+q Load Indirect With Displacement Rd (Y + q) None 2
LD Rd, Z Load Indirect Rd (Z) None 2
LD Rd, Z+ Load Indirect and Post-Increment Rd (Z), Z Z+1 None 2
LD Rd, -Z Load Indirect and Pre-Decrement Z Z - 1, Rd (Z) None 2
LDD Rd, Z+q Load Indirect With Displacement Rd (Z + q) None 2
STS k, Rr Store Direct to Data Space Rd (k) None 2
ST X, Rr Store Indirect (X) Rr None 2
ST X+, Rr Store Indirect and Post-Increment (X) Rr, X X + 1 None 2
ST -X, Rr Store Indirect and Pre-Decrement X X - 1, (X) Rr None 2
ST Y, Rr Store Indirect (Y) Rr None 2
ST Y+, Rr Store Indirect and Post-Increment (Y) Rr, Y Y + 1 None 2
ST -Y, Rr Store Indirect and Pre-Decrement Y Y - 1, (Y) Rr None 2
Instruction Set Summary (Continued)
Mnemonics Operands Description Operation Flags #Clock
AT94K Family
38
STD Y+q, Rr Store Indirect With Displacement (Y + q) Rr None 2
ST Z, Rr Store Indirect (Z) Rr None 2
ST Z+, Rr Store Indirect and Post-Increment (Z) Rr, Z Z + 1 None 2
ST -Z, Rr Store Indirect and Pre-Decrement Z Z - 1, (Z) Rr None 2
STD Z+q, Rr Store Indirect With Displacement (Z + q) Rr None 2
LPM Load Program Memory R0 (Z) None 3
LPM Rd, Z Load Program Memory Rd (Z) None 3
LPM Rd, Z+ Load Program Memory and Post-
Increment
Rd (Z), Z Z + 1 None 3
IN Rd, A In From I/O Location Rd I/O(A) None 1
OUT A, Rr Out To I/O Location I/O(A) Rr None 1
PUSH Rr Push Register on Stack STACK Rr None 2
POP Rd Pop Register from Stack Rd STACK None 2
Bit and Bit-test Instructions
LSL Rd Logical Shift Left Rd(n+1)Rd(n),Rd(0)0,CRd(7) Z,C,N,V,H 1
LSR Rd Logical Shift Right Rd(n)Rd(n+1),Rd(7)0,CRd(0) Z,C,N,V 1
ROL Rd Rotate Left Through Carry Rd(0)C,Rd(n+1)Rd(n),CRd(7) Z,C,N,V,H 1
ROR Rd Rotate Right Through Carry Rd(7)C,Rd(n)Rd(n+1),CRd(0) Z,C,N,V 1
ASR Rd Arithmetic Shift Right Rd(n) Rd(n+1), n=0..6 Z,C,N,V 1
SWAP Rd Swap Nibbles Rd(3..0) Rd(7..4) None 1
BSET s Flag Set SREG(s) 1SREG(s)1
BCLR s Flag Clear SREG(s) 0 SREG(s) 1
SBI A, b Set Bit in I/O Register I/O(A, b) 1None2
CBI A, b Clear Bit in I/O Register I/O(A, b) 0None2
BST Rr, b Bit Store from Register to T T Rr(b) T 1
BLD Rd, b Bit load from T to Register Rd(b) TNone1
SEC Set Carry C 1C1
CLC Clear Carry C 0 C 1
SEN Set Negative Flag N 1N1
CLN Clear Negative Flag N 0 N 1
SEZ Set Zero Flag Z 1Z1
CLZ Clear Zero Flag Z 0 Z 1
SEI Global Interrupt Enable I 1I1
CLI Global Interrupt Disable I 0 I 1
SES Set Signed Test Flag S 1S1
CLS Clear Signed Test Flag S 0 S 1
Instruction Set Summary (Continued)
Mnemonics Operands Description Operation Flags #Clock
AT94K Family
39
Pin Descriptions
VCC
Supply voltage
GND
Ground
PortD (PD7..PD0)
Port D is an 8-bit bi-directional I/O port with internal programmable pull-up resistors. The Port D output buffers can be pro-
grammed to sink/source either 6 or 20 mA (SCR54 see System Control Register on page 32). As inputs, Port D pins that
are externally pulled low will source current if the programmable pull-up resistors are activated.
The Port D pins are tri-stated when a reset condition becomes active, even if the clock is not running. On lower pin count
packages Port D may not be available. Check the Pin List for details.
PortE (PE7..PE0)
Port E is an 8-bit bi-directional I/O port with internal programmable pull-up resistors. The Port E output buffers can be pro-
grammed to sink/source either 6 or 20 mA (SCR55 see System Control Register on page 32). As inputs, Port E pins that
are externally pulled low will source current if the pull-up resistors are activated.
Port E also serves the functions of various special features. See Table 40 on page 128.
The Port E pins are tri-stated when a reset condition becomes active, even if the clock is not running
RX0
Input (receive) from UART(0) See SCR52
TX0
Output (transmit) from UART(0) See SCR52
RX1
Input (receive) from UART(1) See SCR53
TX1
Output (transmit) from UART(1) See SCR53
SEV Set Twos Complement Overflow V 1V1
CLV Clear Twos Complement Overflow V 0 V 1
SET Set T in SREG T 1T1
CLT Clear T in SREG T 0 T 1
SEH Set Half-carry Flag in SREG H 1H1
CLH Clear Half-carry Flag in SREG H 0 H 1
NOP No Operation None 1
SLEEP Sleep (see specific descr. for Sleep) None 1
WDR Watchdog Reset (see specific descr. for WDR) None 1
Instruction Set Summary (Continued)
Mnemonics Operands Description Operation Flags #Clock
AT94K Family
40
XTAL1
Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
XTAL2
Output from the inverting oscillator amplifier
TOSC1
Input to the inverting timer/counter oscillator amplifier
TOSC2
Output from the inverting timer/counter oscillator amplifier
SCL
2-wire serial input/output clock
SDA
2-wire serial input/output data
AT94K Family
41
Clock Options
Crystal Oscillator
XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier, which can be configured for use as an
on-chip oscillator, as shown in Figure 22. Either a quartz crystal or a ceramic resonator may be used.
Figure 22. Oscillator Connections
External Clock
To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in
Figure 23.
Figure 23. External Clock Drive Configuration
XTAL2
XTAL1
GND
C2
C1
MAX 1 HC BUFFER
HC
RBIAS
XTAL2
XTAL1
GND
NC
EXTERNAL
OSCILLATOR
SIGNAL
AT94K Family
42
No Clock/Oscillator Source
When not in use, for low static IDD, add a pull-down resistor to XTAL1.
Figure 24. No Clock/Oscillator Connections
Timer Oscillator
For the timer oscillator pins, TOSC1 and TOSC2, the crystal is connected directly between the pins. The oscillator is opti-
mized for use with a 32.768 kHz watch crystal. An external clock signal applied to this pin goes through the same amplifier
having a bandwidth of 1 MHz. The external clock signal should therefore be in the range 0 Hz - 1 MHz.
Figure 25. Time Oscillator Connections
Architectural Overview
The AVR uses a Harvard architecture concept with separate memories and buses for program and data. The program
memory is accessed with a single level pipeline. While one instruction is being executed, the next instruction is pre-fetched
from the program memory. This concept enables instructions to be executed in every clock-cycle. The program memory is
in-system programmable SRAM memory. With a few exceptions, AVR instructions have a single 16-bit word format, mean-
ing that every program memory address contains a single 16-bit instruction.
During interrupts and subroutine calls, the return address program counter (PC) is stored on the stack. The stack is effec-
tively allocated in the general data SRAM, and consequently the stack size is only limited by the total SRAM size and the
usage of the SRAM. All user programs must initialize the SP (stack pointer) in the reset routine (before subroutines or inter-
rupts are executed). The 16-bit stack pointer (SP) is read/write accessible in the I/O space.
The data SRAM can be easily accessed through the five different addressing modes supported in the AVR architecture.
A flexible interrupt module has its control registers in the I/O space with an additional global interrupt enable bit in the status
register. All the different interrupts have a separate interrupt vector in the interrupt vector table at the beginning of the pro-
gram memory. The different interrupts have priority in accordance with their interrupt vector position. The lower the
interrupt vector address, the higher the priority.
The memory spaces in the AVR architecture are all linear and regular memory maps.
General-purpose Register File
Figure 26 shows the structure of the 32 x 8 general-purpose working registers in the CPU.
XTAL2
XTAL1
GND
NC
RPD
RPD = 4.7K
TOSC2
TOSC1
C1
C2
RB
RS
C1= 33 pF
C2= 27 pF
RB= 10M
RS= 200K
AT94K Family
43
Figure 26. AVR CPU General-purpose Working Registers
All the register operating instructions in the instruction set have direct- and single-cycle access to all registers. The only
exception is the five constant arithmetic and logic instructions SBCI, SUBI, CPI, ANDI and ORI between a constant and a
register and the LDI instruction for load-immediate constant data. These instructions apply to the second half of the regis-
ters in the register file R16..R31. The general SBC, SUB, CP, AND and OR and all other operations between two
registers or on a single-register apply to the entire register file.
As shown in Figure 26 each register is also assigned a data memory address, mapping them directly into the first 32 loca-
tions of the user Data Space. Although not being physically implemented as SRAM locations, this memory organization
provides great flexibility in access of the registers, as the X, Y and Z registers can be set to index any register in the file.
The 4 Kbytes to 16 Kbytes of data SRAM, as configured during FPSLIC download, are available for general data are imple-
mented starting at address $0060 as follows:
Addresses beyond the maximum amount of data SRAM are unavailable for write or read and will return unknown data if
accessed. Ghost memory is not implemented.
7 0 Addr.
R0 $00
R1 $01
R2 $02
. . .
R13 $0D
General-purpose
Working Registers
R14 $0E
R15 $0F
R16 $10
R17 $11
. . .
R26 $1A AVR X-register Low Byte
R27 $1B AVR X-register High Byte
R28 $1C AVR Y-register Low Byte
R29 $1D AVR Y-register High Byte
R30 $1E AVR Z-register Low Byte
R31 $1F AVR Z-register High Byte
4 Kbytes $0060 : $0FFF
8 Kbytes $0060 : $1FFF
12 Kbytes $0060 : $2FFF
16 Kbytes $0060 : $3FFF
AT94K Family
44
X-register, Y-register and Z-register
The registers R26..R31 have some added functions to their general-purpose usage. These registers are address pointers
for indirect addressing of the SRAM. The three indirect address registers X, Y and Z have functions as fixed displacement,
automatic increment and decrement (see the descriptions for the different instructions).
ALU Arithmetic Logic Unit
The high-performance AVR ALU operates in direct connection with all the 32 general-purpose working registers. Within a
single clock cycle, ALU operations between registers in the register file are executed. The ALU operations are divided into
three main categories arithmetic, logical and bit-functions.
Multiplier Unit
The high-performance AVR Multiplier operates in direct connection with all the 32 general-purpose working registers. This
unit performs 8 x 8 multipliers every two clock cycles. See Multiplier details on page 85.
SRAM Data Memory
External data SRAM (or program) cannot be used with the FPSLIC AT94K family.
The five different addressing modes for the data memory cover: Direct, Indirect with Displacement, Indirect, Indirect with
Pre-decrement and Indirect with Post-increment. In the register file, registers R26 to R31 feature the indirect addressing
pointer registers.
The Indirect with Displacement mode features a 63 address locations reach from the base address given by the Y or
Z-register.
When using register indirect addressing modes with automatic Pre-decrement and Post-increment, the address registers
X, Y and Z are decremented and incremented.
The entire data address space including the 32 general-purpose working registers and the 64 I/O registers are all accessi-
ble through all these addressing modes. See the next section for a detailed description of the different addressing modes.
AT94K Family
45
Program and Data Addressing Modes
The embedded AVR core supports powerful and efficient addressing modes for access to the program memory (SRAM)
and data memory (SRAM, Register File and I/O Memory). This section describes the different addressing modes supported
by the AVR architecture.
Register Direct, Single-register Rd
The operand is contained in register d (Rd).
Register Direct, Two Registers Rd and Rr
Operands are contained in register r (Rr) and d (Rd). The result is stored in register d (Rd).
I/O Direct
Operand address is contained in 6 bits of the instruction word. n is the destination or source register address.
Data Direct
A 16-bit data address is contained in the 16 LSBs of a two-word instruction. Rd/Rr specify the destination or source
register.
Data Indirect with Displacement
Operand address is the result of the Y or Z-register contents added to the address contained in 6 bits of the instruction
word.
Data Indirect
Operand address is the contents of the X, Y or the Z-register.
Data Indirect with Pre-decrement
The X, Y or the Z-register is decremented before the operation. Operand address is the decremented contents of the X, Y
or the Z-register.
Data Indirect with Post-increment
The X, Y or the Z-register is incremented after the operation. Operand address is the content of the X, Y or the Z-register
prior to incrementing.
Direct Program Address, JMP and CALL
Program execution continues at the address immediate in the instruction words.
Indirect Program Addressing, IJMP and ICALL
Program execution continues at address contained by the Z-register (i.e., the PC is loaded with the contents of the
Z-register).
Relative Program Addressing, RJMP and RCALL
Program execution continues at address PC + k + 1. The relative address k is -2048 to 2047.
AT94K Family
46
Memory Access Times and Instruction Execution Timing
This section describes the general access timing concepts for instruction execution and internal memory access.
The AVR CPU is driven by the XTAL1 input directly generated from the external clock crystal for the chip. No internal clock
division is used.
Figure 27 shows the parallel instruction fetches and instruction executions enabled by the Harvard architecture and the
fast-access register file concept. This is the basic pipelining concept to obtain up to 1 MIPS per MHz with the corresponding
unique results for functions per cost, functions per clocks, and functions per power-unit.
Figure 28 shows the internal timing concept for the register file. In a single clock cycle an ALU operation using two register
operands is executed, and the result is stored back to the destination register.
Figure 27. The Parallel Instruction Fetches and Instruction Executions
Figure 28. Single Cycle ALU Operation
AVR CLK
1st Instruction Fetch
1st Instruction Execute
2nd Instruction Fetch
2nd Instruction Execute
3rd Instruction Fetch
3rd Instruction Execute
4th Instruction Fetch
T1 T2 T3 T4
AVR CLK
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
T1 T2 T3 T4
AT94K Family
47
The internal data SRAM access is performed in two system clock cycles as described in Figure 29.
Figure 29. On-chip Data SRAM Access Cycles
Memory-mapped I/O
The I/O space definition of the embedded AVR core is shown in the following table:
AT94K Register Summary
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reference
Page
$3F ($5F) SREG I T H S V N Z C 50
$3E ($5E) SPH SP15 SP14 SP13 SP12 SP11 SP10 SP9 SP8 50
$3D ($5D) SPL SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0 50
$3C ($5C) Reserved
$3B ($5B) EIMF INTF3 INTF2 INTF1 INTF0 INT3 INT2 INT1 INT0 62
$3A ($5A) SFTCR FMXOR WDTS DBG SRST 51
$39 ($59) TIMSK TOIE1 OCIE1A OCIE1B TOIE2 TICIE1 OCIE2 TOIE0 OCIE0 62
$38 ($58) TIFR TOV1 OCF1A OCF1B TOV2 ICF1 OCF2 TOV0 OCF0 63
$37 ($57) Reserved
$36 ($56) TWCR TWINT TWEA TWSTA TWSTO TWWC TWEN TWIE 110
$35 ($55) MCUR SE SM1 SM0 PORF WDRF EXTRF 51
$34 ($54) Reserved
$33 ($53) TCCR0 FOC0 PWM0 COM01 COM00 CTC0 CS02 CS01 CS00 69
$32 ($52) TCNT0 Timer/Counter0 (8-bit) 70
$31 ($51) OCR0 Timer/Counter0 Output Compare Register 71
$30 ($50) SFIOR PSR2 PSR10 66
$2F ($4F) TCCR1A COM1A1 COM1A0 COM1B1 COM1B0 FOC1A FOC1B PWM11 PWM10 76
$2E ($4E) TCCR1B ICNC1 ICES1 ICPE CTC1 CS12 CS11 CS10 77
$2D ($4D) TCNT1H Timer/Counter1 - Counter Register High Byte 78
$2C ($4C) TCNT1L Timer/Counter1 - Counter Register Low Byte 78
$2B ($4B) OCR1AH Timer/Counter1 - Output Compare Register A High Byte 79
$2A ($4A) OCR1AL Timer/Counter1 - Output Compare Register A Low Byte 79
$29 ($49) OCR1BH Timer/Counter1 - Output Compare Register B High Byte 79
$28 ($48) OCR1BL Timer/Counter1 - Output Compare Register B Low Byte 79
AVR CLK
WR
RD
Data
Data
Address Address
T1 T2 T3 T4
Prev. Address
Read Write
AT94K Family
48
$27 ($47) TCCR2 FOC2 PWM2 COM21 COM20 CTC2 CS22 CS21 CS20 69
$26 ($46) ASSR AS2 TCN20B OCR2UB TCR2UB 73
$25 ($45) ICR1H Timer/Counter1 - Input Capture Register High Byte 80
$24 ($44) ICR1L Timer/Counter1 - Input Capture Register Low Byte 80
$23 ($43) TCNT2 Timer/Counter2 (8-bit) 70
$22 ($42) OCR2 Timer/Counter 2 Output Compare Register 71
$21 ($41) WDTCR WDTOE WDE WDP2 WDP1 WDP0 83
$20 ($40) UBRRHI UART1 Baud Rate High Nibble [11..8] UART0 Baud Rate Low Nibble [11..8] 105
$1F ($3F) TWDR 2-wire Serial Data Register 111
$1E ($3E) TWAR 2-wire Serial Address Register 112
$1D ($3D) TWSR 2-wire Serial Status Register 112
$1C ($3C) TWBR 2-wire Serial Bit Rate Register 109
$1B ($3B) FPGAD FPGA Cache Data Register (D7 - D0) 52
$1A ($3A) FPGAZ FPGA Cache Z Address Register (T3 - T0) (Z3 - Z0) 53
$19 ($39) FPGAY FPGA Cache Y Address Register (Y7 - Y0) 53
$18 ($38) FPGAX FPGA Cache X Address Register (X7 - X0) 53
$17 ($37) FISUD FPGA I/O Select, Interrupt Mask/Flag Register D (Reserved on AT94K05) 54, 56
$16 ($36) FISUC FPGA I/O Select, Interrupt Mask/Flag Register C (Reserved on AT94K05) 54, 56
$15 ($35) FISUB FPGA I/O Select, Interrupt Mask/Flag Register B 54, 56
$14 ($34) FISUA FPGA I/O Select, Interrupt Mask/Flag Register A 54, 56
$13 ($33) FISCR FIADR XFIS1 XFIS0 53
$12 ($32) PORTD PORTD7 PORTD6 PORTD5 PORTD4 PORTD3 PORTD2 PORTD1 PORTD0 124
$11 ($31) DDRD DDRD7 DDRD6 DDRD5 DDRD4 DDRD3 DDRD2 DDRD1 DDRD0 124
$10 ($30) PIND PIND7 PIND6 PIND5 PIND4 PIND3 PIND2 PIND1 PIND0 124
$0F ($2F) Reserved
$0E ($2E) Reserved
$0D ($2D) Reserved
$0C ($2C) UDR0 UART0 I/O Data Register 101
$0B ($2B) UCSR0A RXC0 TXC0 UDRE0 FE0 OR0 U2X0 MPCM0 101
$0A ($2A) UCSR0B RXCIE0 TXCIE0 UDRIE0 RXEN0 TXEN0 CHR90 RXB80 TXB80 103
$09 ($29) UBRR0 UART0 Baud-rate Register 105
$08 ($28) Reserved
$07 ($27) PORTE PORTE7 PORTE6 PORTE5 PORTE4 PORTE3 PORTE2 PORTE1 PORTE0 126
$06 ($26) DDRE DDRE7 DDRE6 DDRE5 DDRE4 DDRE3 DDRE2 DDRE1 DDRE0 126
$05 ($25) PINE PINE7 PINE6 PINE5 PINE4 PINE3 PINE2 PINE1 PINE0 126
$04 ($24) Reserved
$03 ($23) UDR1 UART1 I/O Data Register 101
$02 ($22) UCSR1A RXC1 TXC1 UDRE1 FE1 OR1 U2X1 MPCM1 101
$01 ($21) UCSR1B RXCIE1 TXCIE1 UDRIE1 RXEN1 TXEN1 CHR91 RXB81 TXB81 103
$00 ($20) UBRR1 UART1 Baud-rate Register 105
AT94K Register Summary (Continued)
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reference
Page
AT94K Family
49
All the different embedded AVR core I/Os and peripherals are placed in the I/O space. All FPGA virtual peripherals are
placed in the I/O space. The different I/O locations are directly accessed by the IN and OUT instructions transferring data
between the 32 x 8 general-purpose working registers and the I/O space. I/O registers within the address range $00 - $1F
are directly bit-accessible using the SBI and CBI instructions. In these registers, the value of single bits can be checked by
using the SBIS and SBIC instructions. When using the I/O specific instructions IN, OUT, the I/O register address $00 - $3F
are used. When addressing I/O registers as SRAM, $20 must be added to this address. All I/O register addresses through-
out this document are shown with the SRAM address in parentheses.
Figure 30. Memory-mapped I/O
For single-cycle access (In/Out Commands) to I/O, the instruction has to be less than 16 bits:
In the data SRAM, the registers are located at memory addresses $00 - $1F and the I/O space is located at memory
addresses $20 - $5F.
As there are only 6 bits available to refer to the I/O space, the address is shifted down 2 bits. This means the In/Out com-
mands access $00 to $3F which goes directly to the I/O and maps to $20 to $5F in SRAM. All other instructions access the
I/O space through the $20 - $5F addressing.
For compatibility with future devices, reserved bits should be written zero if accessed. Reserved I/O memory addresses
should never be written.
The status flags are cleared by writing a logic 1 to them. Note that the CBI and SBI instructions will operate on all bits in the
I/O register, writing a one back into any flag read as set, thus clearing the flag. The CBI and SBI instructions work with reg-
isters $00 to $1F only.
The different I/O and peripherals control registers are explained in the following sections.
opcode register address
5 bits
r0 - 31 ($1F)
5 bits
r0 - 63 ($3F)
6 bits
$00
$1F
$5F
SRAM Space
I/O Space
$00
$3F Memory-mapped
I/O
Registers r0 - r31
Used for In/Out
Instructions
Used for all
Other Instructions
AT94K Family
50
Status Register SREG
The AVR status register SREG at I/O space location $3F ($5F) is defined as:
Bit 7 - I: Global Interrupt Enable
The global interrupt enable bit must be set (one) for the interrupts to be enabled. The individual interrupt enable control is
then performed in separate control registers. If the global interrupt enable register is cleared (zero), none of the interrupts
are enabled independent of the individual interrupt enable settings. The I-bit is cleared by hardware after an interrupt has
occurred, and is set by the RETI instruction to enable subsequent interrupts.
Bit 6 - T: Bit Copy Storage
The bit copy instructions BLD (Bit LoaD) and BST (Bit STore) use the T-bit as source and destination for the operated bit. A
bit from a register in the register file can be copied into T by the BST instruction, and a bit in T can be copied into a bit in a
register in the register file by the BLD instruction.
Bit 5 - H: Half-carry Flag
The half-carry flag H indicates a half-carry in some arithmetic operations.
Bit 4 - S: Sign Bit, S = N V
The S-bit is always an exclusive or between the negative flag N and the twos complement overflow flag V.
Bit 3 - V: Two’s Complement Overflow Flag
The twos complement overflow flag V supports twos complement arithmetics.
Bit 2 - N: Negative Flag
The negative flag N indicates a negative result from an arithmetical or logical operation.
Bit 1 - Z: Zero Flag
The zero flag Z indicates a zero result from an arithmetical or logical operation.
Bit 0 - C: Carry Flag
The carry flag C indicates a carry in an arithmetical or logical operation.
Note: Note that the status register is not automatically stored when entering an interrupt routine and restored when returning from an
interrupt routine. This must be handled by software.
Stack Pointer SP
The general AVR 16-bit Stack Pointer is effectively built up of two 8-bit registers in the I/O space locations $3E ($5E) and
$3D ($5D). Future versions of FPSLIC may support up to 64 KB memory; therefore, all 16 bits are used.
Bit 76543210
$3F ($5F) I T H S V N Z C SREG
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 1514131211109 8
$3E ($5E) SP15 SP14 SP13 SP12 SP11 SP10 SP9 SP8 SPH
$3D ($5D) SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0 SPL
76543210
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
AT94K Family
51
The Stack Pointer points to the data SRAM stack area where the Subroutine and Interrupt Stacks are located. This Stack
space in the data SRAM must be defined by the program before any subroutine calls are executed or interrupts are
enabled. The stack pointer must be set to point above $60. The Stack Pointer is decremented by one when data is pushed
onto the Stack with the PUSH instruction, and it is decremented by two when an address is pushed onto the Stack with
subroutine calls and interrupts. The Stack Pointer is incremented by one when data is popped from the Stack with the POP
instruction, and it is incremented by two when an address is popped from the Stack with return from subroutine RET or
return from interrupt RETI.
Software Control of System Configuration
The software control register will allow the software to manage select system level configuration bits.
Software Control Register SFTCR
Bits 7..4 - Res: Reserved Bits
These bits are reserved in the AT94K and always read as zero.
Bit 3 - FMXOR: Frame Mode XOR (Enable/Disable)
This bit is XORed with the System Control Registers Enable Frame Interface bit. The behavior when this bit is set to 1 is
dependent on how the SCR was initialized. If the Enable Frame Interface bit in the SCR is 0, the FMXOR bit enables the
Frame Interface when set to 1. If the Enable Frame Interface bit in the SCR is 1, the FMXOR bit disables the Frame Inter-
face when set to 1. During AVR reset, the FMXOR bit is cleared by hardware.
Bit 2 - WDTS: Software Watchdog Test Clock Select
When this bit is set to 1, the test clock signal is selected to replace the AVR internal oscillator into associated watchdog
timer logic. During AVR reset, the WDTS bit is cleared by hardware.
Bit 1 - DBG: Debug Mode (see page 26)
When this bit is set to 1, the AVR can write its own program SRAM. During AVR reset, the DBG bit is cleared by hardware.
Bit 0 - SRST: Software Reset
When this bit is set (one), a reset request is sent to the system configuration external to the AVR. Appropriate reset signals
are generated back into the AVR and configuration download is initiated. A software reset will cause the EXTRF bit in the
MCUR register to be set (one), which remains set throughout the AVR reset and may be read by the restarted program
upon reset complete. The external reset flag is set (one) since the requested reset is issued from the system configuration
external to the AVR core. During AVR reset, the SRST bit is cleared by hardware.
MCU Control Status/Register MCUR
The MCU Register contains control bits for general MCU functions and status bits to indicate the source of an MCU reset.
Bits 7, 6 - Res: Reserved Bits
These bits are reserved in the AT94K and always read as zero.
00000000
Bit 76543210
$3A ($5A) - - - - FMXOR WDTS DBG SRST SFTCR
Read/Write R R R R R/W R/W R/W R/W
Initial Value00000000
Bit 76543210
$35 ($55) - - SE SM1 SM0 PORF WDRF EXTRF MCUR
Read/Write R R R/W R/W R/W R/W R/W R/W
Initial Value00000101
AT94K Family
52
Bit 5 - SE: Sleep Enable
The SE bit must be set (one) to make the MCU enter the Sleep mode when the SLEEP instruction is executed. To avoid
the MCU entering the Sleep mode unless it is the programmers purpose, it is recommended to set the Sleep Enable SE bit
just before the execution of the SLEEP instruction.
Bits 4, 3 - SM1/SM0: Sleep Mode Select Bits 1 and 0
This bit selects between the three available Sleep modes as shown in Table 10.
Bit 2 - PORF: Power-on Reset Flag
This flag is set (one) upon power-up of the device. The flag can only be cleared (zero) by writing a zero to the PORF bit.
The bit will not be cleared by hardware during AVR reset.
Bit 1 - WDRF: Watchdog Reset Flag
This bit is set if a watchdog reset occurs. The bit is cleared by writing a logic 0 to the flag.
Bit 0 - EXTRF: External (Software) Reset Flag
This flag is set (one) in three separate circumstances: power-on reset, use of Resetn/AVRResetn and writing a one to the
SRST bit in the Software Control Register SFTCR. The PORF flag can be checked to eliminate power-on reset as a
cause for this flag to be set. There is no way to differentiate between use of Resetn/AVRResetn and software reset. The
flag can only be cleared (zero) by writing a zero to the EXTRF bit. The bit will not be cleared by hardware during AVR reset.
FPGA Cache Logic
FPGA Cache Data Register FPGAD
The FPGAD I/O Register address is not supported by a physical register; it is simply the I/O address that, if written to, gen-
erates the FPGA Cache I/O write strobe. The CACHEIOWE signal is a qualified version of the AVR IOWE signal. It will only
be active if an OUT or ST (store to) instruction references the FPGAD I/O address. The FPGAD I/O address is write-
sensitive-only; an I/O read to this location is ignored. If the AVR Cache Interface bit in the SCR [BIT62] is set (one), the
data being written to this address is cached to the FPGA address specified by the FPGAX..Z registers (see below) during
the active CACHEIOWE strobe.
Table 10. Sleep Mode Select
SM1 SM0 Sleep Mode
0 0 Idle Mode
01Reserved
1 0 Power-down
1 1 Power-save
Bit 76543210
$1B ($3B) MSB LSB FPGAD
Read/WriteWWWWWWWW
Initial Value N/A N/A N/A N/A N/A N/A N/A N/A
AT94K Family
53
FPGA Cache Z Address Registers FPGAX..Z
The three FPGA Cache address registers combine to form the 24-bit address, CACHEADDR[23:0], delivered to the FPGA
cache logic outside the AVR block during a write to the FPGAD I/O Register (see above).
FPGA I/O Selection by AVR
Sixteen select signals are sent to the FPGA for I/O addressing. These signals are decoded from four I/O registry addresses
(FISU {A, B, C, D}) and extended to sixteen with two bits from the FPGA I/O Select Control Register (FISCR). In addition,
the FPGAIORE and FPGAIOWE signals are qualified versions of the IORE and IOWE signals. Each will only be active if
one of the four base I/O addresses are referenced. It is necessary for the FPGA design to implement any required registers
for each select line; each qualified with either the FPGAIORE or FPGAIOWE strobe. Refer to the FPGA/AVR Interface sec-
tion for more details. Only the FISCR registers physically exist. The FISU {A, B, C, D} I/O addresses for the purpose of
FPGA I/O selection are NOT supported by AVR Core I/O space registers; they are simply I/O addresses (available to 1
cycle IN/OUT instructions) which trigger appropriate enabling of the FPGA select lines and the FPGA IORE/IOWE strobes
(see Figure 16 on page 21).
FPGA I/O Select Control Register FISCR
Bit 7 - FIADR: FPGA Interrupt Addressing Enable
When FIADR is set (one), the four dual-purpose I/O addresses, FISUA..D, are mapped to four physical registers that pro-
vide memory space for FPGA interrupt masking and interrupt flag status. When FIADR is cleared (zero), and I/O read or
write to one of the four dual-purpose I/O addresses, FISUA..D, will access its associated group of four FPGA I/O select
lines. The XFIS1 and XFIS0 bits (see below) further determine which one select line in the accessed group is set (one). A
read will assign the FPGA I/O read enable to the AVR I/O read enable (FPGAIORE IORE) and a write, the FPGA I/O
write enable to the AVR I/O write enable (FPGAIOWE IOWE). FPGA macros utilizing one or more FPGA I/O select lines
must use the FPGA I/O read/write enables, FPGAIORE or FPGAIOWE, to qualify each select line. The FIADR bit will be
cleared (zero) during AVR rest.
Bits 6..2 - Res: Reserved Bits
These bits are reserved and always read as zero.
Bits 1, 0 - XFIS1, 0: Extended FPGA I/O Select Bits 1, 0
XFIS[1:0] determines which one of the four FPGA I/O select lines will be set (one) within the accessed group an I/O read
or write to one of the four dual-purpose I/O addresses, FISUA..D, will access one of four groups. Table 11 details the FPGA
I/O selection scheme.
Bit 76543210
$18 ($38) FCX7 FCX6 FCX5 FCX4 FCX3 FCX2 FCX1 FCX0 FPGAX
$19 ($39) FCY7 FCY6 FCY5 FCY4 FCY3 FCY2 FCY1 FCY0 FPGAY
$1A ($3A) FCT3 FCT2 FCT1 FCT0 FCZ3 FCZ2 FCZ1 FCZ0 FPGAZ
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$13 ($33) FIADR-----XFIS1XFIS0FISCR
Read/WriteR/WRRRRRR/WR/W
Initial Value00000000
AT94K Family
54
In summary, 16 select signals are sent to the FPGA for I/O addressing. These signals are decoded from four base I/O Reg-
ister addresses (FISUA..D) and extended to 16 with two bits from the FPGA I/O Select Control Register, XFIS1 and XFIS0.
The FPGA I/O read and write signals, FPGAIORE and FPGAIOWE, are qualified versions of the AVR IORE and IOWE sig-
nals. Each will only be active if one of the four base I/O addresses is accessed.
Reset: all select lines become active and an FPGAIOWE strobe is enabled. This is to allow the FPGA design to load zeros
(8h00) from the D-bus into appropriate registers.
Table 11. FPGA I/O Select Line Scheme
Read or Write
I/O Address
FISCR Register FPGA I/O Select Lines
XFIS1 XFIS0 15..12 11..8 7..4 3..0
FISUA $14 ($34)
0 0 0000 0000 0000 0001
0 1 0000 0000 0000 0010
1 0 0000 0000 0000 0100
1 1 0000 0000 0000 1000
FISUB $15 ($35)
0 0 0000 0000 0001 0000
0 1 0000 0000 0010 0000
1 0 0000 0000 0100 0000
1 1 0000 0000 1000 0000
FISUC $16 ($36)
(not available on
AT94K05)
0 0 0000 0001 0000 0000
0 1 0000 0010 0000 0000
1 0 0000 0100 0000 0000
1 1 0000 1000 0000 0000
FISUD $17 ($37)
(not available on
AT94K05)
0 0 0001 0000 0000 0000
0 1 0010 0000 0000 0000
1 0 0100 0000 0000 0000
1 1 1000 0000 0000 0000
AT94K Family
55
General AVRFPGA I/O Select Procedure
I/O select depends on the FISCR register setup and the FISUA..D register written to or read from.
The following FISCR setups and writing data to the FISUA..D registers will result in the shown I/O select lines and data pre-
sented on the 8-bit AVRFPGA data bus.
Note: 1. IOSEL 7..0 only available on AT94K05.
;---------------------------------------------
io_select0_write:
ldi r16,0x00 ;FIADR=0,XFIS1=0,XFIS0=0 ->I/O select line=0
out FISCR,r16 ;load I/O select values into FISCR register
out FISUA,r17; ;select line 0 high. Place data on AVR<->FPGA bus
; from r17 register. (out going data is assumed
; to be present in r17 before calling this subroutine)
ret
;---------------------------------------------
io_select13_read:
ldi r16,0x01 ;FIADR=0,XFIS1=0,XFIS0=1 ->I/O select line=13
out FISCR,r16 ;load I/O select values into FISCR register
in r18,FISUD ;select line 13 high. Read data on AVR<->FPGA bus
; which was placed into register FISUD.
ret
Table 12. FISCR Register Setups and I/O Select Lines.
FISCR Register I/O Select Lines(1)
FIADR(b7) b6-2 XFIS1(b1) XFIS0(b0) FISUA FISUB FISUC FISUD
0 - 0 0 IOSEL 0 IOSEL 4 IOSEL 8 IOSEL 12
0 - 0 1 IOSEL 1 IOSEL 5 IOSEL 9 IOSEL 13
0 - 1 0 IOSEL 2 IOSEL 6 IOSEL 10 IOSEL 14
0 - 1 1 IOSEL 3 IOSEL 7 IOSEL 11 IOSEL 15
AT94K Family
56
FPGA I/O Interrupt Control by AVR
This is an alternate memory space for the FPGA I/O Select addresses. If the FIADR bit in the FISCR register is set to logic
1, the four I/O addresses, FISUA - FISUD, are mapped to physical registers and provide memory space for FPGA interrupt
masking and interrupt flag status. If the FIADR bit in the FISCR register is cleared to a logic 0, the I/O register addresses
will be decoded into FPGA select lines.
All FPGA interrupt lines into the AVR are active low. See page 57 for interrupt priority.
Interrupt Control Registers FISUA..D
Bits 7..4 - FIF3 - 0: FPGA Interrupt Flags 3 - 0
Bits 7..4 - FIF7 - 4: FPGA Interrupt Flags 7 - 4
Bits 7..4 - FIF11 - 8: FPGA Interrupt Flags 11 - 8 (not available on AT94K05)
Bits 7..4 - FIF15 - 12: FPGA Interrupt Flags 15 - 12 (not available on AT94K05)
The 16 FPGA interrupt flag bits all work the same. Each is set (one) by a valid negative edge transition on its associated
interrupt line from the FPGA. Valid transitions are defined as any change in state preceded by at least three cycles of the
old state and succeeded by at least three cycles of the new state. Therefore, it is required that interrupt lines transition from
1 to 0 at least three cycles after the line is stable high; the line must then remain stable low for at least three cycles follow-
ing the transition. Each bit is cleared by hardware when executing the corresponding interrupt handling vector.
Alternatively, each bit will be cleared by writing a logic 1 to it. When the I-bit in the Status Register, the corresponding
FPGA interrupt mask bit and the given FPGA interrupt flag bit are set (one), the associated interrupt is executed.
Bits 3..0 - FINT3 - 0: FPGA Interrupt Masks 3 - 0
FPGA interrupts 3 - 0 will cause a wake-up from the AVR Sleep modes.
Bits 3..0 - FINT7 - 4: FPGA Interrupt Masks 7 - 4
Bits 3..0 - FINT11 - 8: FPGA Interrupt Masks 11 - 8 (not available on AT94K05)
Bits 3..0 - FINT15 - 12: FPGA Interrupt Masks 15 -12 (not available on AT94K05)
The 16 FPGA interrupt mask bits all work the same. When a mask bit is set (one) and the I-bit in the Status Register is set
(one), the given FPGA interrupt is enabled. The corresponding interrupt handling vector is executed when the given FPGA
interrupt flag bit is set (one) by a negative edge transition on the associated interrupt line from the FPGA.
Bit 76543210
$14 ($34) FIF3 FIF2 FIF1 FIF0 FINT3 FINT2 FINT1 FINT0 FISUA
$15 ($35) FIF7 FIF6 FIF5 FIF4 FINT7 FINT6 FINT5 FINT4 FSUB
$16 ($36) FIF11 FIF10 FIF9 FIF8 FINT11 FINT10 FINT9 FINT8 FISUC
$17 ($37) FIF15 FIF14 FIF13 FIF12 FINT15 FINT14 FINT13 FINT12 FISUD
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
AT94K Family
57
Reset and Interrupt Handling
The embedded AVR and FPGA core provide 35 different interrupt sources. These interrupts and the separate reset vector
each have a separate program vector in the program memory space. All interrupts are assigned individual enable bits
(masks) which must be set (one) together with the I-bit in the status register in order to enable the interrupt.
The lowest addresses in the program memory space must be defined as the Reset and Interrupt vectors. The complete list
of vectors is shown in Table 13. The list also determines the priority levels of the different interrupts. The lower the address
the higher the priority level. RESET has the highest priority, and next is FPGA_INT0 the FPGA Interrupt Request 0 etc.
Table 13. Reset and Interrupt Vectors
Vector No. (hex) Program Address Source Interrupt Definition
01 $0000 RESET Reset Handle: Program execution starts here
02 $0002 FPGA_INT0 FPGA Interrupt0 Handle
03 $0004 EXT_INT0 External Interrupt0 Handle
04 $0006 FPGA_INT1 FPGA Interrupt1 Handle
05 $0008 EXT_INT1 External Interrupt1 Handle
06 $000A FPGA_INT2 FPGA Interrupt2 Handle
07 $000C EXT_INT2 External Interrupt2 Handle
08 $000E FPGA_INT3 FPGA Interrupt3 Handle
09 $0010 EXT_INT3 External Interrupt3 Handle
0A $0012 TIM2_COMP Timer/Counter2 Compare Match Interrupt Handle
0B $0014 TIM2_OVF Timer/Counter2 Overflow Interrupt Handle
0C $0016 TIM1_CAPT Timer/Counter1 Capture Event Interrupt Handle
0D $0018 TIM1_COMPA Timer/Counter1 Compare Match A Interrupt Handle
0E $001A TIM1_COMPB Timer/Counter1 Compare Match B Interrupt Handle
0F $001C TIM1_OVF Timer/Counter1 Overflow Interrupt Handle
10 $001E TIM0_COMP Timer/Counter0 Compare Match Interrupt Handle
11 $0020 TIM0_OVF Timer/Counter0 Overflow Interrupt Handle
12 $0022 FPGA_INT4 FPGA Interrupt4 Handle
13 $0024 FPGA_INT5 FPGA Interrupt5 Handle
14 $0026 FPGA_INT6 FPGA Interrupt6 Handle
15 $0028 FPGA_INT7 FPGA Interrupt7 Handle
16 $002A UART0_RXC UART0 Receive Complete Interrupt Handle
17 $002C UART0_DRE UART0 Data Register Empty Interrupt Handle
18 $002E UART0_TXC UART0 Transmit Complete Interrupt Handle
19 $0030 FPGA_INT8 FPGA Interrupt8 Handle (not available on AT94K05)
1A $0032 FPGA_INT9 FPGA Interrupt9 Handle (not available on AT94K05)
1B $0034 FPGA_INT10 FPGA Interrupt10 Handle (not available on AT94K05)
1C $0036 FPGA_INT11 FPGA Interrupt11 Handle (not available on AT94K05)
1D $0038 UART1_RXC UART1 Receive Complete Interrupt Handle
1E $003A UART1_DRE UART1 Data Register Empty Interrupt Handle
1F $003C UART1_TXC UART1 Transmit Complete Interrupt Handle
20 $003E FPGA_INT12 FPGA Interrupt12 Handle (not available on AT94K05)
21 $0040 FPGA_INT13 FPGA Interrupt13 Handle (not available on AT94K05)
22 $0042 FPGA_INT14 FPGA Interrupt14 Handle (not available on AT94K05)
23 $0044 FPGA_INT15 FPGA Interrupt15 Handle (not available on AT94K05)
24 $0046 TWS_INT 2-wire Serial Interrupt
AT94K Family
58
The most typical program setup for the Reset and Interrupt Vector Addresses are:
Address Labels Code Comments
$0000 jmp RESET Reset Handle: Program execution starts here
$0002 jmp FPGA_INT0 ; FPGA Interrupt0 Handle
$0004 jmp EXT_INT0 ; External Interrupt0 Handle
$0006 jmp FPGA_INT1 ; FPGA Interrupt1 Handle
$0008 jmp EXT_INT1 ; External Interrupt1 Handle
$000A jmp FPGA_INT2 ; FPGA Interrupt2 Handle
$000C jmp EXT_INT2 ; External Interrupt2 Handle
$000E jmp FPGA_INT3 ; FPGA Interrupt3 Handle
$0010 jmp EXT_INT3 ; External Interrupt3 Handle
$0012 jmp TIM2_COMP ; Timer/Counter2 Compare Match Interrupt Handle
$0014 jmp TIM2_OVF ; Timer/Counter2 Overflow Interrupt Handle
$0016 jmp TIM1_CAPT ; Timer/Counter1 Capture Event Interrupt Handle
$0018 jmp TIM1_COMPA ; Timer/Counter1 Compare Match A Interrupt Handle
$001A jmp TIM1_COMPB ; Timer/Counter1 Compare Match B Interrupt Handle
$001C jmp TIM1_OVF ; Timer/Counter1 Overflow Interrupt Handle
$001E jmp TIM0_COMP ; Timer/Counter0 Compare Match Interrupt Handle
$0020 jmp TIM0_OVF ; Timer/Counter0 Overflow Interrupt Handle
$0022 jmp FPGA_INT4 ; FPGA Interrupt4 Handle
$0024 jmp FPGA_INT5 ; FPGA Interrupt5 Handle
$0026 jmp FPGA_INT6 ; FPGA Interrupt6 Handle
$0028 jmp FPGA_INT7 ; FPGA Interrupt7 Handle
$002A jmp UART0_RXC ; UART0 Receive Complete Interrupt Handle
$002C jmp UART0_DRE ; UART0 Data Register Empty Interrupt Handle
$002E jmp UART0_TXC ; UART0 Transmit Complete Interrupt Handle
$0030 jmp FPGA_INT8 ; FPGA Interrupt8 Handle (not available on AT94K05)
$0032 jmp FPGA_INT9 ; FPGA Interrupt9 Handle (not available on AT94K05)
$0034 jmp FPGA_INT10 ; FPGA Interrupt10 Handle (not available on AT94K05)
$0036 jmp FPGA_INT11 ; FPGA Interrupt11 Handle (not available on AT94K05)
$0038 jmp UART1_RXC ; UART1 Receive Complete Interrupt Handle
$003A jmp UART1_DRE ; UART1 Data Register Empty Interrupt Handle
$003C jmp UART1_TXC ; UART1 Transmit Complete Interrupt Handle
$003E jmp FPGA_INT12 ; FPGA Interrupt12 Handle (not available on AT94K05)
$0040 jmp FPGA_INT13 ; FPGA Interrupt13 Handle (not available on AT94K05)
$0042 jmp FPGA_INT14 ; FPGA Interrupt14 Handle (not available on AT94K05)
$0044 jmp FPGA_INT15 ; FPGA Interrupt15 Handle (not available on AT94K05)
$0046 jmp TWS_INT ; 2-wire Serial Interrupt
;
$0048 RESET: ldi r16, high(RAMEND); Main program start
$0049 out SPH,r16
$004A ldi r16, low(RAMEND)
$004B out SPL,r16
$004C <instr> xxx
... ... ... ...
AT94K Family
59
Reset Sources
The embedded AVR core has four sources of reset:
External Reset. The MCU is reset immediately when a low-level is present on the RESET or AVR RESET pin.
Power-on Reset. The MCU is reset upon chip power-up and remains in reset until the FPGA configuration has entered
Idle mode.
Watchdog Reset. The MCU is reset when the Watchdog Timer period expires and the watchdog is enabled.
Software Reset. The MCU is reset when the SRST bit in the Software Control register is set (one).
During reset, all I/O registers except the MCU Status register are then set to their Initial Values, and the program starts exe-
cution from address $0000. The instruction placed in address $0000 must be a JMP absolute jump instruction to the reset
handling routine. If the program never enables an interrupt source, the interrupt vectors are not used, and regular program
code can be placed at these locations. The circuit diagram in Figure 31 shows the reset logic. Table 14 defines the timing
and electrical parameters of the reset circuitry.
Figure 31. Reset Logic
Note: 1. The Power-on Reset will not work unless the supply voltage has been below VPOT (falling).
MCU STATUS
DATA BUS
RESET/
AVR RESET
WATCHDOG
TIMER
INTERNAL
OSCILLATOR
SYSTEM
CLOCK
DELAY COUNTERS
QS
RINTERNAL
RESET
POR
COUNTER RESET
SEL [4:0] CONTROLLED
BY FPGA CONFIGURATION
FULL
FPGA
CONFIG
LOGIC
EXTRF
WDRF
SFTCR
BIT 0
PORF
Table 14. Reset Characteristics (VCC = 3.3V)
Symbol Parameter Min Typ Max Units
VPOT(1) Power-on Reset Threshold (rising) 1.0 1.4 1.8 V
Power-on Reset Threshold (falling) 0.4 0.6 0.8 V
VRST RESET Pin Threshold Voltage VCC/2 V
TTOUT Reset Delay Time-out Period
5 CPU cycles
0.4
3.2
12.8
0.5
4.0
16.0
0.6
4.8
19.2
ms
AT94K Family
60
Power-on Reset
A Power-on Reset (POR) circuit ensures that the device is reset from power-on. As shown in Figure 31, an internal timer
clocked from the Watchdog Timer oscillator prevents the MCU from starting until after a certain period after VCC has
reached the Power-on Threshold voltage VPOT, regardless of the VCC rise time (see Figures 24 and 25).
Figure 32. MCU Start-up, RESET Tied to VCC
Figure 33. Watchdog Reset during Operation
The MCU after five CPU clock-cycles, and can be used when an external clock signal is applied to the XTAL1 pin. This set-
ting does not use the WDT oscillator, and enables very fast start-up from the Sleep, Power-down or Power-save modes if
the clock signal is present during sleep.
RESET can be connected to VCC directly or via an external pull-up resistor. By holding the pin low for a period after VCC has
been applied, the Power-on Reset period can be extended. Refer to Figure 34 for a timing example on this.
V
RESET
TIME-OUT
INTERNAL
RESET
tTOUT
VPOT
VRST
CC
(HIGH)
RESET (HIGH)
RESET TIME-OUT
INTERNAL RESET
WDT TIME-OUT
tTOUT
1 XTAL CYCLE
V
CC
AT94K Family
61
Figure 34. MCU Start-up, RESET Controlled Externally
External Reset
An external reset is generated by a low-level on the AVRRESET pin. When the applied signal reaches the Reset Threshold
Voltage VRST on its positive edge, the delay timer starts the MCU after the Time-out period tTOUT has expired.
Watchdog Reset
When the Watchdog times out, it will generate a short reset pulse of 1 XTAL cycle duration. On the falling edge of this
pulse, the delay timer starts counting the Time-out period tTOUT. Time-out period tTOUT is approximately 3 µs at VCC =
3.3V. the period of the time out is voltage dependent.
Software Reset
See Software Control of System Configurationon page 51.
Interrupt Handling
The embedded AVR core has one dedicated 8-bit Interrupt Mask control register: TIMSK Timer/Counter Interrupt Mask
Register. In addition, other enable and mask bits can be found in the peripheral control registers.
When an interrupt occurs, the Global Interrupt Enable I-bit is cleared (zero) and all interrupts are disabled. The user soft-
ware can set (one) the I-bit to enable nested interrupts. The I-bit is set (one) when a Return from Interrupt instruction
RETI is executed.
When the Program Counter is vectored to the actual interrupt vector in order to execute the interrupt handling routine, hard-
ware clears the corresponding flag that generated the interrupt. Some of the interrupt flags can also be cleared by writing a
logic 1 to the flag bit position(s) to be cleared.
If an interrupt condition occurs when the corresponding interrupt enable bit is cleared (zero), the interrupt flag will be set
and remembered until the interrupt is enabled, or the flag is cleared by software.
If one or more interrupt conditions occur when the global interrupt enable bit is cleared (zero), the corresponding interrupt
flag(s) will be set and remembered until the global interrupt enable bit is set (one), and will be executed by order of priority.
The status register is not automatically stored when entering an interrupt routine and restored when returning from an inter-
rupt routine. This must be handled by software.
RESET
TIME-OUT
INTERNAL
RESET
tTOUT
VPOT
VRST
V
CC
AT94K Family
62
External Interrupt Mask/Flag Register EIMF
Bits 3..0 - INT3, 2, 1, 0: External Interrupt Request 3, 2, 1, 0 Enable
When an INT3 - INT0 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), the corresponding external pin
interrupt is enabled. The external interrupts are always negative edge triggered interrupts.
Bits 7..4 - INTF3, 2, 1, 0: External Interrupt 3, 2, 1, 0 Flags
When a falling edge is detected on the INT3, 2, 1, 0 pins an interrupt request is triggered. The corresponding interrupt flag,
INTF3, 2, 1, 0 becomes set (one). If the I-bit in SREG and the corresponding interrupt enable bit, INT3, 2, 1, 0 in EIMF, are
set (one), the MCU will jump to the interrupt vector. The flag is cleared when the interrupt routine is executed. Alternatively,
the flag is cleared by writing a logic 1 to it.
Timer/Counter Interrupt Mask Register TIMSK
Bit 7 - TOIE1: Timer/Counter1 Overflow Interrupt Enable
When the TOIE1 bit is set (one) and the I-bit in the Status Register is set (one), the Timer/Counter1 Overflow interrupt is
enabled. The corresponding interrupt is executed if an overflow in Timer/Counter1 occurs, i.e., when the TOV1 bit is set in
the Timer/Counter Interrupt Flag Register TIFR.
Bit 6 - OCIE1A: Timer/Counter1 Output CompareA Match Interrupt Enable
When the OCIE1A bit is set (one) and the I-bit in the Status Register is set (one), the Timer/Counter1 CompareA Match
interrupt is enabled. The corresponding interrupt is executed if a CompareA match in Timer/Counter1 occurs, i.e., when the
OCF1A bit is set in the Timer/Counter Interrupt Flag Register TIFR.
Bit 5 - OCIE1B: Timer/Counter1 Output CompareB Match Interrupt Enable
When the OCIE1B bit is set (one) and the I-bit in the Status Register is set (one), the Timer/Counter1 CompareB Match
interrupt is enabled. The corresponding interrupt is executed if a CompareB match in Timer/Counter1 occurs, i.e., when the
OCF1B bit is set in the Timer/Counter Interrupt Flag Register TIFR.
Bit 4 - TOIE2: Timer/Counter2 Overflow Interrupt Enable
When the TOIE2 bit is set (one) and the I-bit in the Status Register is set (one), the Timer/Counter2 overflow interrupt is
enabled. The corresponding interrupt is executed if an overflow in Timer/Counter2 occurs, i.e., when the TOV2 bit is set in
the Timer/Counter interrupt flag register TIFR.
Bit 3 - TICIE1: Timer/Counter1 Input Capture Interrupt Enable
When the TICIE1 bit is set (one) and the I-bit in the Status Register is set (one), the Timer/Counter1 input capture event
interrupt is enabled. The corresponding interrupt is executed if a capture-triggering event occurs on pin 29, (IC1), i.e., when
the ICF1 bit is set in the Timer/Counter interrupt flag register TIFR.
Bit 2 - OCIE2: Timer/Counter2 Output Compare Interrupt Enable
When the OCIE2 bit is set (one) and the I-bit in the Status Register is set (one), the Timer/Counter2 Compare Match inter-
rupt is enabled. The corresponding interrupt is executed if a Compare match in Timer/Counter2 occurs, i.e., when the
OCF2 bit is set in the Timer/Counter interrupt flag register TIFR.
Bit 76543210
$3B ($5B) INTF3 INTF2 INTF1 INTF0 INT3 INT2 INT1 INT0 EIMF
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$39 ($39) TOIE1 OCIE1A OCIE1B TOIE2 TICIE1 OCIE2 TOIE0 OCIE0 TIMSK
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
AT94K Family
63
Bit 1 - TOIE0: Timer/Counter0 Overflow Interrupt Enable
When the TOIE0 bit is set (one) and the I-bit in the Status Register is set (one), the Timer/Counter0 Overflow interrupt is
enabled. The corresponding interrupt is executed if an overflow in Timer/Counter0 occurs, i.e., when the TOV0 bit is set in
the Timer/Counter Interrupt Flag Register TIFR.
Bit 0 - OCIE0: Timer/Counter0 Output Compare Interrupt Enable
When the OCIE0 bit is set (one) and the I-bit in the Status Register is set (one), the Timer/Counter0 Compare Match inter-
rupt is enabled. The corresponding interrupt is executed if a Compare match in Timer/Counter0 occurs, i.e., when the
OCF0 bit is set in the Timer/Counter Interrupt Flag Register TIFR.
Timer/Counter Interrupt Flag Register TIFR
Bit 7 - TOV1: Timer/Counter1 Overflow Flag
The TOV1 is set (one) when an overflow occurs in Timer/Counter1. TOV1 is cleared by hardware when executing the cor-
responding interrupt handling vector. Alternatively, TOV1 is cleared by writing a logic 1 to the flag. When the I-bit in SREG,
and TOIE1 (Timer/Counter1 Overflow Interrupt Enable), and TOV1 are set (one), the Timer/Counter1 Overflow Interrupt is
executed. In PWM mode, this bit is set when Timer/Counter1 advances from $0000.
Bit 6 - OCF1A: Output Compare Flag 1A
The OCF1A bit is set (one) when compare match occurs between the Timer/Counter1 and the data in OCR1A Output
Compare Register 1A. OCF1A is cleared by hardware when executing the corresponding interrupt handling vector. Alterna-
tively, OCF1A is cleared by writing a logic 1 to the flag. When the I-bit in SREG, and OCIE1A (Timer/Counter1 Compare
Interrupt Enable), and the OCF1A are set (one), the Timer/Counter1 Compare A match Interrupt is executed.
Bit 5 - OCF1B: Output Compare Flag 1B
The OCF1B bit is set (one) when compare match occurs between the Timer/Counter1 and the data in OCR1B Output
Compare Register 1B. OCF1B is cleared by hardware when executing the corresponding interrupt handling vector. Alterna-
tively, OCF1B is cleared by writing a logic 1 to the flag. When the I-bit in SREG, and OCIE1B (Timer/Counter1 Compare
match Interrupt Enable), and the OCF1B are set (one), the Timer/Counter1 Compare B match Interrupt is executed.
Bit 4 - TOV2: Timer/Counter2 Overflow Flag
The TOV2 bit is set (one) when an overflow occurs in Timer/Counter2. TOV2 is cleared by hardware when executing the
corresponding interrupt handling vector. Alternatively, TOV2 is cleared by writing a logic 1 to the flag. When the I-bit in
SREG, and TOIE2 (Timer/Counter1 Overflow Interrupt Enable), and TOV2 are set (one), the Timer/Counter2 Overflow
Interrupt is executed. In PWM mode, this bit is set when Timer/Counter2 advances from $00.
Bit 3 - ICF1: Input Capture Flag 1
The ICF1 bit is set (one) to flag an input capture event, indicating that the Timer/Counter1 value has been transferred to the
input capture register ICR1. ICF1 is cleared by hardware when executing the corresponding interrupt handling vector.
Alternatively, ICF1 is cleared by writing a logic 1 to the flag. When the SREG I-bit, and TICIE1 (Timer/Counter1 Input Cap-
ture Interrupt Enable), and ICF1 are set (one), the Timer/Counter1 Capture Interrupt is executed.
Bit 2 - OCF2: Output Compare Flag 2
The OCF2 bit is set (one) when compare match occurs between Timer/Counter2 and the data in OCR2 Output Compare
Register 2. OCF2 is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, OCF2
is cleared by writing a logic 1 to the flag. When the I-bit in SREG, and OCIE2 (Timer/Counter2 Compare Interrupt Enable),
and the OCF2 are set (one), the Timer/Counter2 Output Compare Interrupt is executed.
Bit 76543210
$38 ($58) TOV1 OCF1A OCF1B TOV2 ICF1 OCF2 TOV0 OCF0 TIFR
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
AT94K Family
64
Bit 1 - TOV0: Timer/Counter0 Overflow Flag
The bit TOV0 is set (one) when an overflow occurs in Timer/Counter0. TOV0 is cleared by hardware when executing the
corresponding interrupt handling vector. Alternatively, TOV0 is cleared by writing a logic 1 to the flag. When the SREG I-bit,
and TOIE0 (Timer/Counter0 Overflow Interrupt Enable), and TOV0 are set (one), the Timer/Counter0 Overflow interrupt is
executed. In PWM mode, this bit is set when Timer/Counter0 advances from $00.
Bit 0 - OCF0: Output Compare Flag 0
The OCF0 bit is set (one) when compare match occurs between Timer/Counter0 and the data in OCR0 Output Compare
Register 0. OCF0 is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, OCF0
is cleared by writing a logic 1 to the flag. When the I-bit in SREG, and OCIE0 (Timer/Counter2 Compare Interrupt Enable),
and the OCF0 are set (one), the Timer/Counter0 Output Compare Interrupt is executed.
Interrupt Response Time
The interrupt execution response for all the enabled AVR interrupts is four clock cycles minimum. Four clock cycles after
the interrupt flag has been set, the program vector address for the actual interrupt handling routine is executed. During this
four clock-cycle period, the Program Counter (2 bytes) is pushed onto the Stack, and the Stack Pointer is decremented by
2. The vector is normally a jump to the interrupt routine, and this jump takes three clock cycles. If an interrupt occurs during
execution of a multi-cycle instruction, this instruction is completed before the interrupt is served.
A return from an interrupt handling routine (same as for a subroutine call routine) takes four clock cycles. During these four
clock cycles, the Program Counter (2 bytes) is popped back from the Stack, and the Stack Pointer is incremented by 2.
When the AVR exits from an interrupt, it will always return to the main program and execute one more instruction before
any pending interrupt is served.
Sleep Modes
To enter any of the three Sleep modes, the SE bit in MCUR must be set (one) and a SLEEP instruction must be executed.
The SM1 and SM0 bits in the MCUR register select which Sleep mode (Idle, Power-down, or Power-save) will be activated
by the SLEEP instruction, see Table 10 on page 52.
If an enabled interrupt occurs while the MCU is in a Sleep mode, the MCU awakes, executes the interrupt routine, and
resumes execution from the instruction following SLEEP. The contents of the register file, SRAM, and I/O memory are unal-
tered. If a reset occurs during Sleep mode, the MCU wakes up and executes from the Reset vector
Idle Mode
When the SM1/SM0 bits are set to 00, the SLEEP instruction makes the MCU enter the Idle mode, stopping the CPU but
allowing UARTs, Timer/Counters, Watchdog 2-wire Serial and the Interrupt System to continue operating. This enables the
MCU to wake-up from external triggered interrupts as well as internal ones like the Timer Overflow and UART Receive
Complete interrupts. When the MCU wakes up from Idle mode, the CPU starts program execution immediately.
Power-down Mode
When the SM1/SM0 bits are set to 10, the SLEEP instruction makes the MCU enter the Power-down mode. In this mode,
the external oscillator is stopped, while the external interrupts and the watchdog (if enabled) continue operating. Only an
external reset, a watchdog reset (if enabled), or an external level interrupt can wake-up the MCU.
Note that if a level-triggered interrupt is used for wake-up from Power-down mode, the changed level must be held for
some time to wake-up the MCU. This makes the MCU less sensitive to noise. The changed level is sampled twice by the
watchdog oscillator clock, and if the input has the required level during this time, the MCU will wake-up. The period of the
watchdog oscillator is 1 µs (nominal) at 3.3V and 25°C. The frequency of the watchdog oscillator is voltage dependent.
When waking up from Power-down mode, there is a delay from the wake-up condition occurs until the wake-up becomes
effective. This allows the clock to restart and become stable after having been stopped. The wake-up period is defined by
the same time-set bits that define the reset time-out period. The wake-up period is equal to the clock reset period, as
shown in Table 15.
If the wake-up condition disappears before the MCU wakes up and starts to execute, e.g., a low-level on is not held long
enough, the interrupt causing the wake-up will not be executed.
AT94K Family
65
Power-save Mode
When the SM1/SM0 bits are 11, the SLEEP instruction makes the MCU enter the Power-save mode. This mode is identical
to power-down, with one exception:
If Timer/Counter2 is clocked asynchronously, i.e., the AS2 bit in ASSR is set, Timer/Counter2 will run during sleep. In addi-
tion to the power-down wake-up sources, the device can also wake-up from either Timer Overflow or Output Compare
event from Timer/Counter2 if the corresponding Timer/Counter2 interrupt enable bits are set in TIMSK. To ensure that the
part executes the Interrupt routine when waking up, also set the global interrupt enable bit in SREG.
When waking up from Power-save mode by an external interrupt, two instruction cycles are executed before the interrupt
flags are updated. When waking up by the asynchronous timer, three instruction cycles are executed before the flags are
updated. During these cycles, the processor executes instructions, but the interrupt condition is not readable, and the inter-
rupt routine has not started yet.
See Table 2 on page 15 for clock activity during Power-down, Power-save and Idle modes.
Timer/Counters
The FPSLIC provides three general-purpose Timer/Counters two 8-bit T/Cs and one 16-bit T/C. Timer/Counter2 can
optionally be asynchronously clocked from an external oscillator. This oscillator is optimized for use with a 32.768 kHz
watch crystal, enabling use of Timer/Counter2 as a Real-time Clock (RTC). Timer/Counters 0 and 1 have individual pres-
caling selection from the same 10-bit prescaling timer. Timer/Counter2 has its own prescaler. Both these prescalers can be
reset by setting the corresponding control bits in the Special Functions I/O Register (SFIOR). Refer to page 66 for a
detailed description. These Timer/Counters can either be used as a timer with an internal clock time-base or as a counter
with an external pin connection which triggers the counting.
Timer/Counter Prescalers
Figure 35. Prescaler for Timer/Counter0 and 1
PSR10
Clear
TCK1 TCK0
AT94K Family
66
For Timer/Counters 0 and 1, the four prescaled selections are: CK/8, CK/64, CK/256 and CK/1024, where CK is the oscilla-
tor clock. For the two Timer/Counters 0 and 1, CK, external source, and stop, can also be selected as clock sources.
Setting the PSR10 bit in SFIOR resets the prescaler. This allows the user to operate with a predictable prescaler. Note that
Timer/Counter1 and Timer/Counter0 share the same prescaler and a prescaler reset will affect both Timer/Counters.
Figure 36. Timer/Counter2 Prescaler
The clock source for Timer/Counter2 prescaler is named PCK2. PCK2 is by default connected to the main system clock
CK. By setting the AS2 bit in ASSR, Timer/Counter2 is asynchronously clocked from the TOSC1 pin. This enables use of
Timer/Counter2 as a Real-time Clock (RTC). When AS2 is set, pins TOSC1 and TOSC2 are disconnected from Port D. A
crystal can then be connected between the TOSC1 and TOSC2 pins to serve as an independent clock source for
Timer/Counter2. The oscillator is optimized for use with a 32.768 kHz crystal. Alternatively, an external clock signal can be
applied to TOSC1. The frequency of this clock must be lower than one fourth of the CPU clock and not higher than 1 MHz.
Setting the PSR2 bit in SFIOR resets the prescaler. This allows the user to operate with a predictable prescaler.
Special Function I/O Register SFIOR
Bits 7..2 - Res: Reserved Bits
These bits are reserved bits in the FPSLIC and always read as zero.
Bit 1 - PSR2: Prescaler Reset Timer/Counter2
When this bit is set (one) the Timer/Counter2 prescaler will be reset. The bit will be cleared by hardware after the operation
is performed. Writing a zero to this bit will have no effect. This bit will always be read as zero if Timer/Counter2 is clocked
by the internal CPU clock. If this bit is written when Timer/Counter2 is operating in asynchronous mode; however, the bit
will remain as one until the prescaler has been reset. See Asynchronous Operation of Timer/Counter2on page 74 for a
detailed description of asynchronous operation.
Bit 76543210
$30 ($50) - - - - - - PSR2 PSR10 SFIOR
Read/WriteRRRRRRR/WR/W
Initial Value 0 0 0 0 0 0 0 0
10-BIT T/C PRESCALER
TIMER/COUNTER2 CLOCK SOURCE
CK PCK2
TOSC1
AS2
CS20
CS21
CS22
PCK2/8
PCK2/64
PCK2/128
PCK2/1024
PCK2/256
PCK2/32
0
PSR2
Clear
TCK2
AT94K Family
67
Bit 0 - PSR10: Prescaler Reset Timer/Counter1 and Timer/Counter0
When this bit is set (one) the Timer/Counter1 and Timer/Counter0 prescaler will be reset. The bit will be cleared by hard-
ware after the operation is performed. Writing a zero to this bit will have no effect. Note that Timer/Counter1 and
Timer/Counter0 share the same prescaler and a reset of this prescaler will affect both timers. This bit will always be read as
zero.
8-bit Timers/Counters T/C0 and T/C2
Figure 37 shows the block diagram for Timer/Counter0. Figure 38 shows the block diagram for Timer/Counter2.
Figure 37. Timer/Counter0 Block Diagram
8-BIT DATA BUS
TIMER INT. FLAG
REGISTER (TIFR)
TIMER/COUNTER0
(TCNT0)
8-BIT COMPARATOR
OUTPUT COMPARE
REGISTER0 (OCR0)
TIMER INT. MASK
REGISTER (TIMSK)
0
0
0
7
7
7
T/C CLK SOURCE
UP/DOWN
T/C CLEAR
CONTROL
LOGIC
TOV1
OCF1B
OCF1A
ICF1
TOV2
OCF2
OCF0
TOV0
CK
T/C0 OVER-
FLOW IRQ
T/C0 COMPARE
MATCH IRQ
OCF0
TOV0
TOIE0
TOIE1
OCIE1A
OCIE1B
TICIE1
TOIE2
OCIE2
OCIE0
T/C0 CONTROL
REGISTER (TCCR0)
CS02
COM01
PWM0
CS01
COM00
CS00
CTC0
FOC0
PSR2
PSR10
SPECIAL FUNCTIONS
IO REGISTER (SFIOR)
T0
AT94K Family
68
Figure 38. Timer/Counter2 Block Diagram
The 8-bit Timer/Counter0 can select clock source from CK, prescaled CK, or an external pin.
The 8-bit Timer/Counter2 can select clock source from CK, prescaled CK or external TOSC1.
Both Timers/Counters can be stopped as described in section Timer/Counter0 Control Register TCCR0on page 69 and
Timer/Counter2 Control Register TCCR2on page 69
The various status flags (overflow and compare match) are found in the Timer/Counter Interrupt Flag Register TIFR. Con-
trol signals are found in the Timer/Counter Control Register TCCR0 and TCCR2. The interrupt enable/disable settings
are found in the Timer/Counter Interrupt Mask Register TIMSK.
When Timer/Counter0 is externally clocked, the external signal is synchronized with the oscillator frequency of the CPU. To
assure proper sampling of the external clock, the minimum time between two external clock transitions must be at least one
internal CPU clock period. The external clock signal is sampled on the rising edge of the internal CPU clock.
The 8-bit Timer/Counters feature both a high-resolution and a high-accuracy usage with the lower prescaling opportunities.
Similarly, the high prescaling opportunities make the Timer/Counter0 useful for lower speed functions or exact-timing func-
tions with infrequent actions.
Timer/Counters 0 and 2 can also be used as 8-bit Pulse Width Modulators (PWM). In this mode, the Timer/Counter and
the output compare register serve as a glitch-free, stand-alone PWM with centered pulses. Refer to page 71 for a detailed
description on this function.
8-BIT DATA BUS
8-BIT ASYNCH T/C2 DATA BUS
ASYNCH. STATUS
REGISTER (ASSR)
TIMER INT. FLAG
REGISTER (TIFR)
TIMER/COUNTER2
(TCNT2)
SYNCH UNIT
8-BIT COMPARATOR
OUTPUT COMPARE
REGISTER2 (OCR2)
TIMER INT. MASK
REGISTER (TIMSK)
0
0
0
7
7
7
T/C CLK SOURCE
UP/DOWN
T/C CLEAR
CONTROL
LOGIC
OCF2
TOV2
TOIE0
TOIE1
OCIE1A
OCIE1B
TICIE1
TOIE2
OCIE2
OCR2UB
TC2UB
ICR2UB
TOSC1
CK
TCK2
T/C2 OVER-
FLOW IRQ
T/C2 COMPARE
MATCH IRQ
AS2
TOV1
OCF1B
OCF1A
ICF1
TOV2
OCF2
OCF0
TOV0
OCIE0
T/C2 CONTROL
REGISTER (TCCR2)
CS22
COM21
PWM2
CS21
COM20
CS20
CTC2
FOC2
PSR2
PSR10
SPECIAL FUNCTIONS
IO REGISTER (SFIOR)
CK
AT94K Family
69
Timer/Counter0 Control Register TCCR0
Timer/Counter2 Control Register TCCR2
Bit 7 - FOC0/FOC2: Force Output Compare
Writing a logic 1 to this bit, forces a change in the compare match output pin PE1 (Timer/Counter0) and PE3
(Timer/Counter2) according to the values already set in COMn1 and COMn0. If the COMn1 and COMn0 bits are written in
the same cycle as FOC0/FOC2, the new settings will not take effect until next compare match or Forced Output Compare
match occurs. The Force Output Compare bit can be used to change the output pin without waiting for a compare match in
the timer. The automatic action programmed in COMn1 and COMn0 happens as if a Compare Match had occurred, but no
interrupt is generated and the Timer/Counters will not be cleared even if CTC0/CTC2 is set. The FOC0/FOC2 bits will
always be read as zero. The setting of the FOC0/FOC2 bits has no effect in PWM mode.
Bit 6 - PWM0/PWM2: Pulse Width Modulator Enable
When set (one) this bit enables PWM mode for Timer/Counter0 or Timer/Counter2. This mode is described on page 71.
Bits 5,4 - COM01, COM00/COM21, COM20: Compare Output Mode, Bits 1 and 0
The COMn1 and COMn0 control bits determine any output pin action following a compare match in Timer/Counter0 or
Timer/Counter2. Output pin actions affect pins PE1(OC0) or PE3(OC2). This is an alternative function to an I/O port, and
the corresponding direction control bit must be set (one) to control an output pin. The control configuration is shown in
Table 15.
Notes: 1. In PWM mode, these bits have a different function. Refer to Table 18 for a detailed description.
2. n = 0 or 2
Bit 3 - CTC0/CTC2: Clear Timer/Counter on Compare Match
When the CTC0 or CTC2 control bit is set (one), Timer/Counter0 or Timer/Counter2 is reset to $00 in the CPU clock-cycle
after a compare match. If the control bit is cleared, Timer/Counter continues counting and is unaffected by a compare
match. When a prescaling of 1 is used, and the compare register is set to C, the timer will count as follows if CTC0/CTC2
is set:
... | C-1 | C | 0 | 1 | ...
When the prescaler is set to divide by 8, the timer will count like this:
... | C-1, C-1, C-1, C-1, C-1, C-1, C-1, C-1 | C, C, C, C, C, C, C, C | 0, 0, 0, 0, 0, 0, 0, 0 | 1, 1, 1, ...
Bit 76543210
$33 ($53) FOC0 PWM0 COM01 COM00 CTC0 CS02 CS01 CS00 TCCR0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$27 ($47) FOC2 PWM2 COM21 COM20 CTC2 CS22 CS21 CS20 TCCR2
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Table 15. Compare Output Mode Select(1)
COMn1 COMn0 Description
0 0 Timer/Counter disconnected from output pin OCn(2)
0 1 Toggle the OCn(2) output line.
1 0 Clear the OCn(2) output line (to zero).
1 1 Set the OCn(2) output line (to one).
AT94K Family
70
In PWM mode, this bit has a different function. If the CTC0 or CTC2 bit is cleared in PWM mode, the Timer/Counter acts as
an up/down counter. If the CTC0 or CTC2 bit is set (one), the Timer/Counter wraps when it reaches $FF. Refer to page 71
for a detailed description.
Bits 2,1,0 - CS02, CS01, CS00/ CS22, CS21, CS20: Clock Select Bits 2,1 and 0
The Clock Select bits 2,1 and 0 define the prescaling source of Timer/Counter0 and Timer/Counter2.
The Stop condition provides a Timer Enable/Disable function. The prescaled modes are scaled directly from the CK oscilla-
tor clock for Timer/Counter0 and PCK2 for Timer/Counter2. If the external pin modes are used for Timer/Counter0,
transitions on PE0/(T0) will clock the counter even if the pin is configured as an output. This feature can give the user SW
control of the counting.
Table 16. Clock 0 Prescale Select
CS02 CS01 CS00 Description
0 0 0 Stop, the Timer/Counter0 is stopped.
001CK
010CK/8
011CK/64
100CK/256
101CK/1024
1 1 0 External Pin PE0(T0), Falling Edge
1 1 1 External Pin PE0(T0), Rising Edge
Table 17. Clock 2 Prescale Select
CS22 CS21 CS20 Description
0 0 0 Stop, the Timer/Counter2 is stopped.
0 0 1 PCK2
0 1 0 PCK2/8
0 1 1 PCK2/32
1 0 0 PCK2/64
1 0 1 PCK2/128
1 1 0 PCK2/256
1 1 1 PCK2/1024
AT94K Family
71
Timer Counter0 TCNT0
Timer/Counter2 TCNT2
These 8-bit registers contain the value of the Timer/Counters.
Both Timer/Counters are realized as up or up/down (in PWM mode) counters with read and write access. If the
Timer/Counter is written to and a clock source is selected, it continues counting in the timer clock cycle following the write
operation.
Timer/Counter0 Output Compare Register OCR0
Timer/Counter2 Output Compare Register OCR2
The output compare registers are 8-bit read/write registers. The Timer/Counter Output Compare Registers contains the
data to be continuously compared with the Timer/Counter. Actions on compare matches are specified in TCCR0 and
TCCR2. A compare match does only occur if the Timer/Counter counts to the OCR value. A software write that sets
Timer/Counter and Output Compare Register to the same value does not generate a compare match.
A compare match will set the compare interrupt flag in the CPU clock-cycle following the compare event.
Timer/Counter 0 and 2 in PWM Mode
When PWM mode is selected, the Timer/Counter either wraps (overflows) when it reaches $FF or it acts as an up/down
counter.
If the up/down mode is selected, the Timer/Counter and the Output Compare Registers OCR0 or OCR2 form an 8-bit,
free-running, glitch-free and phase correct PWM with outputs on the PE1(OC0/PWM0) or PE3(OC2/PWM2) pin.
If the overflow mode is selected, the Timer/Counter and the Output Compare Registers OCR0 or OCR2 form an 8-bit,
free-running and glitch-free PWM, operating with twice the speed of the up/down counting mode.
PWM Modes (Up/Down and Overflow)
The two different PWM modes are selected by the CTC0 or CTC2 bit in the Timer/Counter Control Registers TCCR0 or
TCCR2 respectively.
If CTC0/CTC2 is cleared and PWM mode is selected, the Timer/Counter acts as an up/down counter, counting up from $00
to $FF, where it turns and counts down again to zero before the cycle is repeated. When the counter value matches the
Bit 76543210
$32 ($52) MSB LSB TCNT0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$23 ($43) MSB LSB TCNT2
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$31 ($51) MSB LSB OCR0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$22 ($42) MSB LSB OCR2
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
AT94K Family
72
contents of the Output Compare Register, the PE1(OC0/PWM0) or PE3(OC2/PWM2) pin is set or cleared according to the
settings of the COMn1/COMn0 bits in the Timer/Counter Control Registers TCCR0 or TCCR2.
If CTC0/CTC2 is set and PWM mode is selected, the Timer/Counters will wrap and start counting from $00 after reaching
$FF. The PE1(OC0/PWM0) or PE3(OC2/PWM2) pin will be set or cleared according to the settings of COMn1/COMn0 on
a Timer/Counter overflow or when the counter value matches the contents of the Output Compare Register. Refer to
Table 18 for details.
Notes: 1. n = 0 or 2
2. x = don t care
Note that in PWM mode, the value to be written to the Output Compare Register is first transferred to a temporary location,
and then latched into the OCR when the Timer/Counter reaches $FF. This prevents the occurrence of odd-length PWM
pulses (glitches) in the event of an unsynchronized OCR0 or OCR2 write. See Figure 39 and Figure 40 for examples.
Figure 39. Effects of Unsynchronized OCR Latching in Up/Down Mode
Note: 1. n = 0 or 2 (Figure 39 and Figure 40)
Table 18. Compare Mode Select in PWM Mode
CTCn(1) COMn1(1) COMn0(1) Effect on Compare Pin Frequency
x(2) 0x
(2) Not Connected
01 1
Cleared on compare match, up-counting. Set on compare match,
down-counting (non-inverted PWM) fTCK0/2/510
01 1
Cleared on compare match, down-counting. Set on compare match,
up-counting (inverted PWM) fTCK0/2/510
1 1 0 Cleared on Compare Match, Set on Overflow fTCK0/2/256
1 1 1 Set on Compare Match, Set on Overflow fTCK0/2/256
PWM Output OCn(1
)
PWM Output OCn(1
)
Unsynchronized OCn(1) Latch
Synchronized OCn(1) Latch
Compare Value changes
Counter Value
Compare Value
Glitch
Counter Value
Compare Value
Compare Value changes
AT94K Family
73
Figure 40. Effects of Unsynchronized OCR Latching in Overflow Mode.
Note: 1. n = 0 or 2 (Figure 39 and Figure 40)
During the time between the write and the latch operation, a read from the Output Compare Registers will read the contents
of the temporary location. This means that the most recently written value always will read out of OCR0 and OCR2.
When the Output Compare Register contains $00 or $FF, and the up/down PWM mode is selected, the output
PE1(OC0/PWM0)/PE3(OC2/PWM2) is updated to low or high on the next compare match according to the settings of
COMn1/COMn0. This is shown in Table 19. In overflow PWM mode, the output PE1(OC0/PWM0)/PE3(OC2/PWM2) is held
Low or High only when the Output Compare Register contains $FF.
Notes: 1. n overflow PWM mode, the table above is only valid for OCRn = $FF
2. n = 0 or 2
In up/down PWM mode, the Timer Overflow Flag, TOV0 or TOV2, is set when the counter advances from $00. In overflow
PWM mode, the Timer Overflow Flag is set as in normal Timer/Counter mode. Timer Overflow Interrupts 0 and 2 operate
exactly as in normal Timer/Counter mode, i.e. they are executed when TOV0 or TOV2 are set provided that Timer Overflow
Interrupt and global interrupts are enabled. This does also apply to the Timer Output Compare flag and interrupt.
Asynchronous Status Register ASSR
Bit 7..4 - Res: Reserved Bits
These bits are reserved bits in the FPSLIC and always read as zero.
Table 19. PWM Outputs OCRn = $00 or $FF(1)
COMn1(2) COMn0(2) OCRn(2) Output PWMn(2)
10$00 L
10$FF H
11$00 H
11$FF L
Bit 76543210
$26 ($46) - - - - AS2 TCN2UB OCR2UB TCR2UB ASSR
Read/Write R R R R R/W R R R
Initial Value 0 0 0 0 0 0 0 0
PWM Output OCn
(1
)
PWM Output OCn
(1
)
Unsynchronized OCn
(1)
Latch
Synchronized OCn
(1)
Latch
Counter Value
Compare Value
Counter Value
Compare Value
Compare Value changes
Compare Value changes
Glitch
AT94K Family
74
Bit 3 - AS2: Asynchronous Timer/Counter2 Mode
When this bit is cleared (zero) Timer/Counter2 is clocked from the internal system clock, CK. If AS2 is set, the
Timer/Counter2 is clocked from the TOSC1 pin. When the value of this bit is changed the contents of TCNT2, OCR2 and
TCCR2 might get corrupted.
Bit 2 - TCN2UB: Timer/Counter2 Update Busy
When Timer/Counter2 operates asynchronously and TCNT2 is written, this bit becomes set (one). When TCNT2 has been
updated from the temporary storage register, this bit is cleared (zero) by hardware. A logic 0 in this bit indicates that TCNT2
is ready to be updated with a new value.
Bit 1 - OCR2UB: Output Compare Register2 Update Busy
When Timer/Counter2 operates asynchronously and OCR2 is written, this bit becomes set (one). When OCR2 has been
updated from the temporary storage register, this bit is cleared (zero) by hardware. A logic 0 in this bit indicates that OCR2
is ready to be updated with a new value.
Bit 0 - TCR2UB: Timer/Counter Control Register2 Update Busy
When Timer/Counter2 operates asynchronously and TCCR2 is written, this bit becomes set (one). When TCCR2 has been
updated from the temporary storage register, this bit is cleared (zero) by hardware. A logic 0 in this bit indicates that
TCCR2 is ready to be updated with a new value.
If a write is performed to any of the three Timer/Counter2 registers while its update busy flag is set (one), the updated value
might get corrupted and cause an unintentional interrupt to occur.
The mechanisms for reading TCNT2, OCR2, and TCCR2 are different. When reading TCNT2, the actual timer value is
read. When reading OCR2 or TCCR2, the value in the temporary storage register is read.
Asynchronous Operation of Timer/Counter2
When Timer/Counter2 operates asynchronously, some considerations must be taken:
When switching between asynchronous and synchronous clocking of Timer/Counter2, the timer registers TCNT2, OCR2
and TCCR2 might get corrupted. A safe procedure for switching the clock source is:
1. Disable the Timer/Counter2 interrupts by clearing OCIE2 and TOIE2.
2. Select clock source by setting AS2 as appropriate.
3. Write new values to TCNT2, OCR2, and TCCR2.
4. To switch to asynchronous operation: Wait for TCN2UB, OCR2UB, and TCR2UB.
5. Enable interrupts, if needed.
The oscillator is optimized for use with a 32.768 kHz watch crystal. An external clock signal applied to this pin goes
through the same amplifier having a bandwidth of 256 kHz. The external clock signal should therefore be in the interval
0 Hz - 1 MHz. The frequency of the clock signal applied to the TOSC1 pin must be lower than one fourth of the CPU
main clock frequency.
When writing to one of the registers TCNT2, OCR2, or TCCR2, the value is transferred to a temporary register, and
latched after two positive edges on TOSC1. The user should not write a new value before the contents of the temporary
register have been transferred to its destination. Each of the three mentioned registers have their individual temporary
register, which means that, e.g., writing to TCNT2 does not disturb an OCR2 write in progress. To detect that a transfer
to the destination register has taken place, an Asynchronous Status Register ASSR has been implemented.
When entering Power-save mode after having written to TCNT2, OCR2, or TCCR2, the user must wait until the written
register has been updated if Timer/Counter2 is used to wake-up the device. Otherwise, the MCU will go to sleep before
the changes have had any effect. This is extremely important if the Output Compare2 interrupt is used to wake-up the
device; Output compare is disabled during write to OCR2 or TCNT2. If the write cycle is not finished (i.e., the MCU enters
Sleep mode before the OCR2UB bit returns to zero), the device will never get a compare match and the MCU will not
wake-up.
If Timer/Counter2 is used to wake-up the device from Power-save mode, precautions must be taken if the user wants to
re-enter Power-save mode: The interrupt logic needs one TOSC1 cycle to be reset. If the time between wake-up and
AT94K Family
75
reentering Power-save mode is less than one TOSC1 cycle, the interrupt will not occur and the device will fail to
wake up. If the user is in doubt whether the time before re-entering power-save is sufficient, the following algorithm can
be used to ensure that one TOSC1 cycle has elapsed:
1. Write a value to TCCR2, TCNT2, or OCR2
2. Wait until the corresponding Update Busy flag in ASSR returns to zero.
3. Enter Power-save mode
When asynchronous operation is selected, the 32.768 kHz oscillator for Timer/Counter2 is always running, except in
Power-down mode. After a power-up reset or wake-up from power-down, the user should be aware of the fact that this
oscillator might take as long as one second to stabilize. Therefore, the contents of all Timer2 registers must be
considered lost after a wake-up from power-down, due to the unstable clock signal. The user is advised to wait for at
least one second before using Timer/Counter2 after power-up or wake-up from power-down.
Description of wake-up from Power-save mode when the timer is clocked asynchronously: When the interrupt condition
is met, the wake-up process is started on the following cycle of the timer clock, that is, the timer is always advanced by at
least one before the processor can read the counter value. The interrupt flags are updated three processor cycles after
the processor clock has started. During these cycles, the processor executes instructions, but the interrupt condition is
not readable, and the interrupt routine has not started yet.
During asynchronous operation, the synchronization of the interrupt flags for the asynchronous timer takes three
processor cycles plus one timer cycle. The timer is therefore advanced by at least one before the processor can read the
timer value causing the setting of the interrupt flag. The output compare pin is changed on the timer clock and is not
synchronized to the processor clock.
AT94K Family
76
Timer/Counter1
Figure 41 shows the block diagram for Timer/Counter1.
Figure 41. Timer/Counter1 Block Diagram
The 16-bit Timer/Counter1 can select clock source from CK, prescaled CK, or an external pin. In addition it can be stopped
as described in section Timer/Counter1 Control Register B TCCR1Bon page 78. The different status flags (overflow,
compare match and capture event) are found in the Timer/Counter Interrupt Flag Register TIFR. Control signals are
found in the Timer/Counter1 Control Registers TCCR1A and TCCR1B. The interrupt enable/disable settings for
Timer/Counter1 are found in the Timer/Counter Interrupt Mask Register TIMSK.
When Timer/Counter1 is externally clocked, the external signal is synchronized with the oscillator frequency of the CPU. To
assure proper sampling of the external clock, the minimum time between two external clock transitions must be at least one
internal CPU clock period. The external clock signal is sampled on the rising edge of the internal CPU clock.
The 16-bit Timer/Counter1 features both a high-resolution and a high-accuracy usage with the lower prescaling opportuni-
ties. Similarly, the high-prescaling opportunities makes the Timer/Counter1 useful for lower speed functions or exact-timing
functions with infrequent actions.
The Timer/Counter1 supports two Output Compare functions using the Output Compare Register 1 A and B OCR1A and
OCR1B as the data sources to be compared to the Timer/Counter1 contents. The Output Compare functions include
optional clearing of the counter on compareA match, and actions on the Output Compare pins on both compare matches.
TOIE0
TOIE1
OCIE1A
OCIE1B
TICIE1
TOIE2
OCIE2
OCIE0
TOV0
TOV1
OCF1A
OCF1B
ICF1
TOV2
OCF2
OCF0
TIMER INT. FLAG
REGISTER (TIFR)
CONTROL
LOGIC
TIMER/COUNTER1 (TCNT1)
TIMER INT. MASK
REGISTER (TIMSK)
T/C1 INPUT CAPTURE REGISTER (ICR1)
T/C1 OVER-
FLOW IRQ
T/C1 COMPARE
MATCHA IRQ
T/C1 COMPARE
MATCHB IRQ
T/C1 INPUT
CAPTURE IRQ
8-BIT DATA BUS
16 BIT COMPARATOR
TIMER/COUNTER1 OUTPUT COMPARE REGISTER A
16 BIT COMPARATOR
TIMER/COUNTER1 OUTPUT COMPARE REGISTER B
CAPTURE
TRIGGER
CK
07815
07815
07815
07815 07815
07815
T/C CLEAR
T/C CLOCK SOURCE
UP/DOWN
T/C1 CONTROL
REGISTER A (TCCR1A)
T/C1 CONTROL
REGISTER B (TCCR1B)
FOC1A
FOC1B
COM1A1
COM1A0
COM1B1
COM1B0
PWM11
PWM10
ICNC1
ICES1
CTC1
CS12
CS11
CS10
PSR2
PSR10
SPECIAL FUNCTIONS
IO REGISTER (SFIOR)
TOV1
OCF1B
OCF1A
ICF1
TOV2
OCF2
OCF0
TOV0
T1
AT94K Family
77
Timer/Counter1 can also be used as a 8-, 9- or 10-bit Pulse Width Modulator. In this mode, the counter and the
OCR1A/OCR1B registers serve as a dual-glitch-free stand-alone PWM with centered pulses. Alternatively, the
Timer/Counter1 can be configured to operate at twice the speed in PWM mode, but without centered pulses. Refer to
page 81 for a detailed description on this function.
The Input Capture function of Timer/Counter1 provides a capture of the Timer/Counter1 contents to the Input Capture
Register ICR1, triggered by an external event on the Input Capture Pin PE7(ICP). The actual capture event settings are
defined by the Timer/Counter1 Control Register TCCR1B.
Figure 42. ICP Pin Schematic Diagram
If the noise canceler function is enabled, the actual trigger condition for the capture event is monitored over four samples,
and all four must be equal to activate the capture flag.
Timer/Counter1 Control Register A TCCR1A
Bits 7,6 - COM1A1, COM1A0: Compare Output Mode1A, Bits 1 and 0
The COM1A1 and COM1A0 control bits determine any output pin action following a compare match in Timer/Counter1.
Any output pin actions affect pin OC1A Output CompareA pin PE6. This is an alternative function to an I/O port, and the
corresponding direction control bit must be set (one) to control an output pin. The control configuration is shown in
Table 20.
Bits 5,4 - COM1B1, COM1B0: Compare Output Mode1B, Bits 1 and 0
The COM1B1 and COM1B0 control bits determine any output pin action following a compare match in Timer/Counter1.
Any output pin actions affect pin OC1B Output CompareB pin PE5. This is an alternative function to an I/O port, and the
corresponding direction control bit must be set (one) to control an output pin. The following control configuration is given:
Notes: 1. In PWM mode, these bits have a different function. Refer to Table 24 for a detailed description.
2. X = A or B
Bit 76543210
$2F ($4F) COM1A1 COM1A0 COM1B1 COM1B0 FOC1A FOC1B PWM11 PWM10 TCCR1A
Read/Write R/W R/W R/W R/W R/w R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Table 20. Compare 1 Mode Select(1)
COM1X1(2) COM1X0(2) Description
0 0 Timer/Counter1 Disconnected From Output Pin OC1X
0 1 Toggle the OC1X output line.
1 0 Clear the OC1X output line (to zero).
1 1 Set the OC1X output line (to one).
ICPE
ICPE: Input Capture Pin Enable
AT94K Family
78
Bit 3 - FOC1A: Force Output Compare1A
Writing a logic 1 to this bit forces a change in the compare match output pin PE6 according to the values already set in
COM1A1 and COM1A0. If the COM1A1 and COM1A0 bits are written in the same cycle as FOC1A, the new settings will
not take effect until next compare match or forced compare match occurs. The Force Output Compare bit can be used to
change the output pin without waiting for a compare match in the timer. The automatic action programmed in COM1A1 and
COM1A0 happens as if a Compare Match had occurred, but no interrupt is generated and it will not clear the timer even if
CTC1 in TCCR1B is set. The FOC1A bit will always be read as zero. The setting of the FOC1A bit has no effect in PWM
mode.
Bit 2 - FOC1B: Force Output Compare1B
Writing a logic 1 to this bit forces a change in the compare match output pin PE5 according to the values already set in
COM1B1 and COM1B0. If the COM1B1 and COM1B0 bits are written in the same cycle as FOC1B, the new settings will
not take effect until next compare match or forced compare match occurs. The Force Output Compare bit can be used to
change the output pin without waiting for a compare match in the timer. The automatic action programmed in COM1B1 and
COM1B0 happens as if a Compare Match had occurred, but no interrupt is generated. The FOC1B bit will always be read
as zero. The setting of the FOC1B bit has no effect in PWM mode.
Bits 1..0 - PWM11, PWM10: Pulse Width Modulator Select Bits
These bits select PWM operation of Timer/Counter1 as specified in Table 21. This mode is described on page 81.
Timer/Counter1 Control Register B TCCR1B
Bit 7 - ICNC1: Input Capture1 Noise Canceler (4 CKs)
When the ICNC1 bit is cleared (zero), the input capture trigger noise canceler function is disabled. The input capture is trig-
gered at the first rising/falling edge sampled on the PE7(ICP) input capture pin as specified. When the ICNC1 bit is set
(one), four successive samples are measures on the PE7(ICP) input capture pin, and all samples must be high/low
according to the input capture trigger specification in the ICES1 bit. The actual sampling frequency is XTAL clock
frequency.
Bit 6 - ICES1: Input Capture1 Edge Select
While the ICES1 bit is cleared (zero), the Timer/Counter1 contents are transferred to the Input Capture Register ICR1
on the falling edge of the input capture pin PE7(ICP). While the ICES1 bit is set (one), the Timer/Counter1 contents are
transferred to the Input Capture Register ICR1 on the rising edge of the input capture pin PE7(ICP).
Bit 5 - ICPE: Input Captive Pin Enable
This bit must be set by the user to enable the Input Capture Function of timer1. Disabling prevents unnecessary register
copies during normal use of the PE7 port.
Table 21. PWM Mode Select
PWM11 PWM10 Description
0 0 PWM operation of Timer/Counter1 is Disabled
0 1 Timer/Counter1 is an 8-bit PWM
1 0 Timer/Counter1 is a 9-bit PWM
1 1 Timer/Counter1 is a 10-bit PWM
Bit 76543210
$2E ($4E) ICNC1 ICES1 ICPE - CTC1 CS12 CS11 CS10 TCCR1B
Read/Write R/W R/W R/W R R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
AT94K Family
79
Bit 4 - Res: Reserved Bit
This bit is reserved in the FPSLIC and will always read zero.
Bit 3 - CTC1: Clear Timer/Counter1 on Compare Match
When the CTC1 control bit is set (one), the Timer/Counter1 is reset to $0000 in the clock cycle after a compareA match. If
the CTC1 control bit is cleared, Timer/Counter1 continues counting and is unaffected by a compare match. When a pres-
caling of 1 is used, and the compareA register is set to C, the timer will count as follows if CTC1 is set:
... | C-1 | C | 0 | 1 | ...
When the prescaler is set to divide by 8, the timer will count like this:
... | C-1, C-1, C-1, C-1, C-1, C-1, C-1, C-1 | C, C, C, C, C, C, C, C | 0, 0, 0, 0, 0, 0, 0, 0 | ...
In PWM mode, this bit has a different function. If the CTC1 bit is cleared in PWM mode, the Timer/Counter1 acts as an
up/down counter. If the CTC1 bit is set (one), the Timer/Counter wraps when it reaches the TOP value. Refer to page 81 for
a detailed description.
Bits 2,1,0 - CS12, CS11, CS10: Clock Select1, Bits 2, 1 and 0
The Clock Select1 bits 2,1 and 0 define the prescaling source of Timer/Counter1.
The Stop condition provides a Timer Enable/Disable function. The CK down-divided modes are scaled directly from the CK
oscillator clock. If the external pin modes are used for Timer/Counter1, transitions on PE4/(T1) will clock the counter even if
the pin is configured as an output. This feature can give the user SW control of the counting.
Timer/Counter1 Register TCNT1H AND TCNT1L
This 16-bit register contains the prescaled value of the 16-bit Timer/Counter1. To ensure that both the high and low bytes
are read and written simultaneously when the CPU accesses these registers, the access is performed using an 8-bit tem-
porary register (TEMP). This temporary register is also used when accessing OCR1A, OCR1B and ICR1. If the main
program and also interrupt routines perform access to registers using TEMP, interrupts must be disabled during access
from the main program and interrupt routines.
Table 22. Clock 1 Prescale Select
CS12 CS11 CS10 Description
0 0 0 Stop, the Timer/Counter1 is stopped.
001CK
010CK/8
011CK/64
100CK/256
101CK/1024
1 1 0 External Pin PE4 (T1), Falling Edge
1 1 1 External Pin PE4 (T1), Rising Edge
Bit 1514131211109 8
$2D ($4D) MSB TCNT1H
$2C ($4C) LSB TCNT1L
76543210
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
00000000
AT94K Family
80
TCNT1 Timer/Counter1 Write
When the CPU writes to the high byte TCNT1H, the written data is placed in the TEMP register. Next, when the CPU writes
the low byte TCNT1L, this byte of data is combined with the byte data in the TEMP register, and all 16 bits are written to the
TCNT1 Timer/Counter1 register simultaneously. Consequently, the high byte TCNT1H must be accessed first for a full
16-bit register write operation.
TCNT1 Timer/Counter1 Read
When the CPU reads the low byte TCNT1L, the data of the low byte TCNT1L is sent to the CPU and the data of the high
byte TCNT1H is placed in the TEMP register. When the CPU reads the data in the high byte TCNT1H, the CPU receives
the data in the TEMP register. Consequently, the low byte TCNT1L must be accessed first for a full 16-bit register read
operation.
The Timer/Counter1 is realized as an up or up/down (in PWM mode) counter with read and write access. If Timer/Counter1
is written to and a clock source is selected, the Timer/Counter1 continues counting in the timer clock-cycle after it is preset
with the written value.
Timer/Counter1 Output Compare Register OCR1AH AND OCR1AL
Timer/Counter1 Output Compare Register OCR1BH AND OCR1BL
The output compare registers are 16-bit read/write registers.
The Timer/Counter1 Output Compare Registers contain the data to be continuously compared with Timer/Counter1.
Actions on compare matches are specified in the Timer/Counter1 Control and Status register. A compare match does only
occur if Timer/Counter1 counts to the OCR value. A software write that sets TCNT1 and OCR1A or OCR1B to the same
value does not generate a compare match.
A compare match will set the compare interrupt flag in the CPU clock cycle following the compare event.
Since the Output Compare Registers OCR1A and OCR1B are 16-bit registers, a temporary register TEMP is used
when OCR1A/B are written to ensure that both bytes are updated simultaneously. When the CPU writes the high byte,
OCR1AH or OCR1BH, the data is temporarily stored in the TEMP register. When the CPU writes the low byte, OCR1AL or
OCR1BL, the TEMP register is simultaneously written to OCR1AH or OCR1BH. Consequently, the high byte OCR1AH or
OCR1BH must be written first for a full 16-bit register write operation.
The TEMP register is also used when accessing TCNT1, and ICR1. If the main program and also interrupt routines perform
access to registers using TEMP, interrupts must be disabled during access from the main program and interrupt routines.
Bit 1514131211109 8
$2B ($4B) MSB OCR1AH
$2A ($4A) LSB OCR1AL
76543210
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
00000000
Bit 1514131211109 8
$29 ($49) MSB OCR1BH
$28 ($48) LSB OCR1BL
76543210
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
00000000
AT94K Family
81
Timer/Counter1 Input Capture Register ICR1H AND ICR1L
The input capture register is a 16-bit read-only register.
When the rising or falling edge (according to the input capture edge setting ICES1) of the signal at the input capture pin
PE7(ICP) is detected, the current value of the Timer/Counter1 Register TCNT1 is transferred to the Input Capture Reg-
ister ICR1. In the same cycle, the input capture flag ICF1 is set (one).
Since the Input Capture Register ICR1 is a 16-bit register, a temporary register TEMP is used when ICR1 is read to
ensure that both bytes are read simultaneously. When the CPU reads the low byte ICR1L, the data is sent to the CPU and
the data of the high byte ICR1H is placed in the TEMP register. When the CPU reads the data in the high byte ICR1H, the
CPU receives the data in the TEMP register. Consequently, the low byte ICR1L must be accessed first for a full 16-bit reg-
ister read operation.
The TEMP register is also used when accessing TCNT1, OCR1A and OCR1B. If the main program and also interrupt rou-
tines perform access to registers using TEMP, interrupts must be disabled during access from the main program and
interrupt routine.
Timer/Counter1 in PWM Mode
When the PWM mode is selected, Timer/Counter1 and the Output Compare Register1A OCR1A and the Output Com-
pare Register1B OCR1B, form a dual 8-, 9- or 10-bit, free-running, glitch-free and phase correct PWM with outputs on the
PD6(OC1A) and PE5(OC1B) pins. In this mode the Timer/Counter1 acts as an up/down counter, counting up from $0000 to
TOP (see Table 23), where it turns and counts down again to zero before the cycle is repeated. When the counter value
matches the contents of the 8, 9 or 10 least significant bits (depends of the resolution) of OCR1A or OCR1B, the
PD6(OC1A)/PE5(OC1B) pins are set or cleared according to the settings of the COM1A1/COM1A0 or COM1B1/COM1B0
bits in the Timer/Counter1 Control Register TCCR1A. Refer to Table 24 for details.
Alternatively, the Timer/Counter1 can be configured to a PWM that operates at twice the speed as in the mode described
above. Then the Timer/Counter1 and the Output Compare Register1A OCR1A and the Output Compare Register1B
OCR1B, form a dual 8-, 9- or 10-bit, free-running and glitch-free PWM with outputs on the PE6(OC1A) and PE5(OC1B)
pins.
Bit 1514131211109 8
$25 ($45) MSB ICR1H
$24 ($44) LSB ICR1L
76543210
Read/WriteRRRRRRRR
RRRRRRRR
Initial Value 0 0 0 0 0 0 0 0
00000000
Table 23. Timer TOP Values and PWM Frequency
CTC1 PWM11 PWM10 PWM Resolution Timer TOP value Frequency
0 0 1 8-bit $00FF (255) fTCK1/510
0 1 0 9-bit $01FF (511) fTCK1/1022
0 1 1 10-bit $03FF(1023) fTCK1/2046
1 0 1 8-bit $00FF (255) fTCK1/256
1 1 0 9-bit $01FF (511) fTCK1/512
1 1 1 10-bit $03FF(1023) fTCK1/1024
AT94K Family
82
As shown in Table 23, the PWM operates at either 8-, 9- or 10-bit resolution. Note the unused bits in OCR1A, OCR1B and
TCNT1 will automatically be written to zero by hardware. For example, bit 9 to 15 will be set to zero in OCR1A, OCR1B and
TCNT1 if the 9-bit PWM resolution is selected. This makes it possible for the user to perform read-modify-write operations
in any of the three resolution modes and the unused bits will be treated as dont care.
Notes: 1. X = A or B
2. x = dont care
Note that in the PWM mode, the 8, 9 or 10 least significant OCR1A/OCR1B bits (depends of resolution), when written, are
transferred to a temporary location. They are latched when Timer/Counter1 reaches the value TOP. This prevents the
occurrence of odd-length PWM pulses (glitches) in the event of an unsynchronized OCR1A/OCR1B write. See Figure 43
and Figure 44 for an example in each mode.
Figure 43. Effects on Unsynchronized OCR1 Latching
Note: 1. X = A or B
Table 24. Compare1 Mode Select in PWM Mode
CTC1(1) COM1X1(1) COM1X0(1) Effect on OCX1
x(2) 0x
(2) Not Connected
01 0
Cleared on compare match, up-counting. Set on compare match,
down-counting (non-inverted PWM)
01 1
Cleared on compare match, down-counting. Set on compare match,
up-counting (inverted PWM)
1 1 0 Cleared on Compare Match, Set on Pverflow
1 1 1 Set on Compare Match, Set on Pverflow
Counter Value
Compare V
alue
PWM OutputOC1X(1)
Synchronized OCR1X(1) Latch
Counter Value
Compare Value
PWM OutputOC1X(1)
Unsynchronized OCR1X(1) Latch Glitch
Compare Value changes
Compare Value changes
AT94K Family
83
Figure 44. Effects of Unsynchronized OCR1 Latching in Overflow Mode.
Note: 1. X = A or B
During the time between the write and the latch operation, a read from OCR1A or OCR1B will read the contents of the tem-
porary location. This means that the most recently written value always will read out of OCR1A/B.
When the OCR1X contains $0000 or TOP, and the up/down PWM mode is selected, the output OC1A/OC1B is updated to
low or high on the next compare match according to the settings of COM1A1/COM1A0 or COM1B1/COM1B0. This is
shown in Table 25. In overflow PWM mode, the output OC1A/OC1B is held low or high only when the Output Compare
Register contains TOP.
Notes: 1. In overflow PWM mode, this table is only valid for OCR1X = TOP.
2. X = A or B
In up/down PWM mode, the Timer Overflow Flag1, TOV1, is set when the counter advances from $0000. In overflow PWM
mode, the Timer Overflow flag is set as in normal Timer/Counter mode. Timer Overflow Interrupt1 operates exactly as in
normal Timer/Counter mode, i.e., it is executed when TOV1 is set provided that Timer Overflow Interrupt1 and global inter-
rupts are enabled. This does also apply to the Timer Output Compare1 flags and interrupts.
Table 25. PWM Outputs OCR1X = $0000 or TOP(1)
COM1X1(2) COM1X0(2) OCR1X(2) Output OC1X(2)
1 0 $0000 L
10TOP H
1 1 $0000 H
11TOP L
PWM Output OC1x
(1)
PWM Output OC1x
(1)
Unsynchronized OC1x
(1)
Latch
Synchronized OC1x
(1)
Latch
AT94K Family
84
Watchdog Timer
The Watchdog Timer is clocked from a separate on-chip oscillator which runs at 1 MHz. This is the typical value at VCC =
3.3V. See characterization data for typical values at other VCC levels. By controlling the Watchdog Timer prescaler, the
watchdog reset interval can be adjusted, see Table 26 on page 85 for a detailed description. The WDR (watchdog reset)
instruction resets the Watchdog Timer. Eight different clock cycle periods can be selected to determine the reset period. If
the reset period expires without another watchdog reset, the FPSLIC resets and executes from the reset vector. For timing
details on the watchdog reset,
To prevent unintentional disabling of the watchdog, a special turn-off sequence must be followed when the watchdog is dis-
abled. Refer to the description below for details.
Figure 45. Watchdog Timer
Watchdog Timer Control Register WDTCR
Bits 7..5 - Res: Reserved Bits
These bits are reserved bits in the FPSLIC and will always read as zero.
Bit 4 - WDTOE: Watchdog Turn-off Enable
This bit must be set (one) when the WDE bit is cleared. Otherwise, the watchdog will not be disabled. Once set, hardware
will clear this bit to zero after four clock cycles. Refer to the description of the WDE bit for a watchdog disable procedure.
Bit 3 - WDE: Watchdog Enable
When the WDE is set (one) the Watchdog Timer is enabled, and if the WDE is cleared (zero) the Watchdog Timer function
is disabled. WDE can only be cleared if the WDTOE bit is set(one). To disable an enabled the Watchdog Timer, the follow-
ing procedure must be followed:
1. In the same operation, write a logic 1 to WDTOE and WDE. A logic 1 must be written to WDE even though it is
set to one before the disable operation starts.
2. Within the next four clock cycles, write a logic 0 to WDE. This disables the watchdog.
Bit 76543210
$21 ($41) - - - WDTOE WDE WDP2 WDP1 WDP0 WDTCR
Read/Write R R R R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
AT94K Family
85
Bits 2..0 - WDP2, WDP1, WDP0: Watchdog Timer Prescaler 2, 1 and 0
The WDP2, WDP1 and WDP0 bits determine the Watchdog Timer prescaling when the Watchdog Timer is enabled. The
different prescaling values and their corresponding Time-out periods are shown in Table 26.
Note: 1. The frequency of the watchdog oscillator is voltage dependent as shown in the Electrical Characteristics section.
The WDR (watchdog reset) instruction should always be executed before the Watchdog Timer is enabled. This ensures that
the reset period will be in accordance with the Watchdog Timer prescale settings. If the Watchdog Timer is enabled without
reset, the Watchdog Timer may not start counting from zero.
Multiplier
The multiplier is capable of multiplying two 8-bit numbers, giving a 16-bit result using only two clock cycles. The multiplier
can handle both signed and unsigned integer and fractional numbers without speed or code size penalty. Below are some
examples of using the multiplier for 8-bit arithmetic.
To be able to use the multiplier, six new instructions are added to the AVR instruction set. These are:
MUL, multiplication of unsigned integers
MULS, multiplication of signed integers
MULSU, multiplication of a signed integer with an unsigned integer
FMUL, multiplication of unsigned fractional numbers
FMULS, multiplication of signed fractional numbers
FMULSU, multiplication of a signed fractional number and with an unsigned fractional number
The MULSU and FMULSU instructions are included to improve the speed and code density for multiplication of 16-bit oper-
ands. The second section will show examples of how to efficiently use the multiplier for 16-bit arithmetic.
The component that makes a dedicated digital signal processor (DSP) specially suitable for signal processing is the
multiply-accumulate (MAC) unit. This unit is functionally equivalent to a multiplier directly connected to an arithmetic logic
unit (ALU). The FPSLIC-based AVR Core is designed to give FPSLIC the ability to effectively perform the same multiply-
accumulate operation.
The multiply-accumulate operation (sometimes referred to as multiply-add operation) has one critical drawback. When add-
ing multiple values to one result variable, even when adding positive and negative values to some extent cancel each
other, the risk of the result variable to overrun its limits becomes evident, i.e. if adding 1 to a signed byte variable that con-
tains the value +127, the result will be -128 instead of +128. One solution often used to solve this problem is to introduce
fractional numbers, i.e. numbers that are less than 1 and greater than or equal to -1. Some issues regarding the use of frac-
tional numbers are discussed.
Table 26. Watchdog Timer Prescale Select
WDP2 WDP1 WDP0
Number of WDT
Oscillator Cycles(1)
Typical Time-out
at VCC = 3.0V
0 0 0 16K cycles 47 ms
0 0 1 32K cycles 94 ms
0 1 0 64K cycles 0.19 s
0 1 1 128K cycles 0.38 s
1 0 0 256K cycles 0.75 s
1 0 1 512K cycles 1.5 s
1 1 0 1,024K cycles 3.0 s
1 1 1 2,048K cycles 6.0 s
AT94K Family
86
A listing of all implementations with key performance specifications is given in Table 27.
8-bit Multiplication
Doing an 8-bit multiply using the hardware multiplier is simple, as the examples in this section will clearly show. Just load
the operands into two registers (or only one for square multiply) and execute one of the multiply instructions. The result will
be placed in register pair R1:R0. However, note that only the MUL instruction does not have register usage restrictions.
Figure 46 shows the valid (operand) register usage for each of the multiply instructions.
Example 1 Basic Usage
The first example shows an assembly code that reads the port B input value and multiplies this value with a constant (5)
before storing the result in register pair R17:R16.
in r16,PINB ; Read pin values
ldi r17,5 ; Load 5 into r17
mul r16,r17 ; r1:r0 = r17 * r16
movw r17:r16,r1:r0; Move the result to the r17:r16
; register pair
Note the use of the MOVW instruction. This example is valid for all of the multiply instructions.
Table 27. Performance Summary
8-bit x 8-bit Routines: Word (Cycles)
UnSigned Multiply 8 x 8 = 16 bits 1 (2)
Signed Multiply 8 x 8 = 16 bits 1 (2)
Fractional Signed/UnSigned Multiply 8 x 8 = 16 bits 1 (2)
Fractional Signed Multiply-accumulate 8 x 8 += 16 bits 3 (4)
16-bit x 16-bit Routines:
Signed/UnSigned Multiply 16 x 16 = 32 bits 6 (9)
UnSigned Multiply 16 x 16 = 32 bits 13 (17)
Signed Multiply 16 x 16 = 32 bits 15 (19)
Signed Multiply-accumulate 16 x 16 += 32 bits 19 (23)
Fractional Signed Multiply 16 x 16 = 32 bits 16 (20)
Fractional Signed Multiply-accumulate 16 x 16 += 32 bits 21 (25)
AT94K Family
87
Figure 46. Valid Register Usage
Example 2 Special Cases
This example shows some special cases of the MUL instruction that are valid.
lds r0,variableA; Load r0 with SRAM variable A
lds r1,variableB; Load r1 with SRAM variable B
mul r1,r0 ; r1:r0 = variable A * variable B
lds r0,variableA; Load r0 with SRAM variable A
mul r0,r0 ; r0:r0 = square(variable A)
Even though the operand is put in the result register pair R1:R0, the operation gives the correct result since R1 and R0 are
fetched in the first clock cycle and the result is stored back in the second clock cycle.
Example 3 Multiply-accumulate Operation
The final example of 8-bit multiplication shows a multiply-accumulate operation. The general formula can be written as:
; r17:r16 = r18 * r19 + r17:r16
in r18,PINB ; Get the current pin value on port B
ldi r19,b ; Load constant b into r19
muls r19,r18 ; r1:r0 = variable A * variable B
add r16,r0 ; r17:r16 += r1:r0
adc r17,r1
Typical applications for the multiply-accumulate operation are FIR (Finite Impulse Response) and IIR (Infinite Impulse
Response) filters, PID regulators and FFT (Fast Fourier Transform). For these applications the FMULS instruction is partic-
ularly useful. The main advantage of using the FMULS instruction instead of the MULS instruction is that the 16-bit result of
the FMULS operation always may be approximated to a (well-defined) 8-bit format, see Using Fractional Numberson
page 91.
R0
R1
R2
R3
R4
R6
R5
R7
R8
R9
R10
R11
R12
R14
R13
R15
R16
R17
R18
R19
R20
R22
R21
R23
R24
R25
R26
R27
R28
R30
R29
R31
MUL
R16
R17
R18
R19
R20
R22
R21
R23
R24
R25
R26
R27
R28
R30
R29
R31
R16
R17
R18
R19
R20
R22
R21
R23
MULS MULSU
FMUL
FMULS
FMULSU
cn() an() bcn1()+×=
AT94K Family
88
16-bit Multiplication
The new multiply instructions are specifically designed to improve 16-bit multiplication. This section presents solutions for
using the hardware multiplier to do multiplication with 16-bit operands.
Figure 47 schematically illustrates the general algorithm for multiplying two 16-bit numbers with a 32-bit result (C = A B).
AH denotes the high byte and AL the low byte of the A operand. CMH denotes the middle high byte and CML the middle
low byte of the result C. Equal notations are used for the remaining bytes.
The algorithm is basic for all multiplication. All of the partial 16-bit results are shifted and added together. The sign exten-
sion is necessary for signed numbers only, but note that the carry propagation must still be done for unsigned numbers.
Figure 47. 16-bit Multiplication, General Algorithm
16-bit x 16-bit = 16-bit Operation
This operation is valid for both unsigned and signed numbers, even though only the unsigned multiply instruction (MUL) is
needed. This is illustrated in Figure 48. A mathematical explanation is given:
When A and B are positive numbers, or at least one of them is zero, the algorithm is clearly correct, provided that the prod-
uct C = A B is less than 216 if the product is to be used as an unsigned number, or less than 215 if the product is to be used
as a signed number.
When both factors are negative, the twos complement notation is used; A = 216 - |A| and B = 216 - |B|:
C = A B = (216 - |A|) (216 - |B|) = |A B| + 232 - 216 (|A| + |B|)
Here we are only concerned with the 16 LSBs; the last part of this sum will be discarded and we will get the (correct) result
C = |A B|.
AH AL BH BL
X
AL * BL
AL * BH
AH * BL
AH * BH
+
+
+
=
CH
CMH CML
CL
(sign ext)
(sign
ext)
(sign
ext)
AT94K Family
89
Figure 48. 16-bit Multiplication, 16-bit Result
When one factor is negative and one factor is positive, for example, A is negative and B is positive:
C = A B = (216 - |A|) |B| = (216 |B|) - |A B| = (216 - |A B|) + 216 (|B| - 1)
The MSBs will be discarded and the correct twos complement notation result will be C = 216 - |A B|.
The product must be in the range 0 C 216 - 1 if unsigned numbers are used, and in the range -215 C 215 - 1 if signed
numbers are used.
When doing integer multiplication in C language, this is how it is done. The algorithm can be expanded to do 32-bit multipli-
cation with 32-bit result.
16-bit x 16-bit = 32-bit Operation
Example 4 Basic Usage 16-bit x 16-bit = 32-bit Integer Multiply
Below is an example of how to call the 16 x 16 = 32 multiply subroutine. This is also illustrated in Figure 49.
ldi R23,HIGH(672)
ldi R22,LOW(672) ; Load the number 672 into r23:r22
ldi R21,HIGH(1844)
ldi R20,LOW(1844); Load the number 1844 into r21:r20
callmul16x16_32 ; Call 16bits x 16bits = 32bits
; multiply routine
AH AL BH BL
X
AL * BL
AL * BH
AH * BL
+
+
=
CLCH
1
2
3
AT94K Family
90
Figure 49. 16-bit Multiplication, 32-bit Result
The 32-bit result of the unsigned multiplication of 672 and 1844 will now be in the registers R19:R18:R17:R16. If
muls16x16_32 is called instead of mul16x16_32, a signed multiplication will be executed. If mul16x16_16 is called, the
result will only be 16 bits long and will be stored in the register pair R17:R16. In this example, the 16-bit result will not be
correct.
16-bit Multiply-accumulate Operation
Figure 50. 16-bit Multiplication, 32-bit Accumulated Result
AH AL BH BL
X
AL * BL
AL * BH
AH * BL
AH * BH
+
+
=
CH
CMH CML
CL
(sign
ext)
(sign
ext)
1 + 2
3
4
AH AL BH BL
X
AL * BL
AL * BH
AH * BL
AH * BH
+
+
+
(sign ext)
(sign
ext)
(sign
ext)
=
CH
CMH CML
CL
+
CH CL ( Old )
( New )
CMH CML
AT94K Family
91
Using Fractional Numbers
Unsigned 8-bit fractional numbers use a format where numbers in the range [0, 2> are allowed. Bits 6 - 0 represent the
fraction and bit 7 represents the integer part (0 or 1), i.e. a 1.7 format. The FMUL instruction performs the same operation
as the MUL instruction, except that the result is left-shifted 1 bit so that the high byte of the 2-byte result will have the same
1.7 format as the operands (instead of a 2.6 format). Note that if the product is equal to or higher than 2, the result will not
be correct.
To fully understand the format of the fractional numbers, a comparison with the integer number format is useful: Table 20
illustrates the two 8-bit unsigned numbers formats. Signed fractional numbers, like signed integers, use the familiar twos
complement format. Numbers in the range [-1, 1> may be represented using this format.
If the byte 1011 0010 is interpreted as an unsigned integer, it will be interpreted as 128 + 32 + 16 + 2 = 178. On the other
hand, if it is interpreted as an unsigned fractional number, it will be interpreted as 1 + 0.25 + 0.125 + 0.015625 = 1.390625.
If the byte is assumed to be a signed number, it will be interpreted as 178 - 256 = -122 (integer) or as 1.390625 - 2 =
-0.609375 (fractional number).
Using the FMUL, FMULS and FMULSU instructions should not be more complex than the MUL, MULS and MULSU
instructions. However, one potential problem is to assign fractional variables right values in a simple way. The fraction 0.75
(= 0.5 + 0.25) will, for example, be 0110 0000 if 8 bits are used.
To convert a positive fractional number in the range [0, 2> (for example 1.8125) to the format used in the AVR, the following
algorithm, illustrated by an example, should be used:
Is there a 1 in the number?
Yes, 1.8125 is higher than or equal to 1.
Byte is now 1xxx xxxx
Is there a 0.5 in the rest?
0.8125 / 0.5 = 1.625
Yes, 1.625 is higher than or equal to 1.
Byte is now 11xx xxxx
Is there a 0.25 in the rest?
0.625 / 0.5 = 1.25
Yes, 1.25 is higher than or equal to 1.
Byte is now 111x xxxx
Is there a 0.125 in the rest?
0.25 / 0.5 = 0.5
No, 0.5 is lower than 1.
Byte is now 1110 xxxx
Is there a 0.0625 in the rest?
0.5 / 0.5 = 1
Yes, 1 is higher than or equal to 1.
Byte is now 1110 1xxx
Since we do not have a rest, the remaining three bits will be zero, and the final result is 1110 1000, which is 1 + 0.5 + 0.25
+ 0.0625 = 1.8125.
Table 28. Comparison of Integer and Fractional Formats
Bit Number 76543210
Unsigned Integer Bit
Significance
27 = 128 26 = 64 25 = 32 24 = 16 23 = 8 22 = 4 21 = 2 20 = 1
Unsigned Fractional
Number Bit Significance
20 = 1 2-1 = 0.5 2-2 = 0.25 2-3 =
0.125
2-4 =
0.0625
2-5 =
0.3125
2-6 =
0.015625
2-7 =
0.0078125
AT94K Family
92
To convert a negative fractional number, first add 2 to the number and then use the same algorithm as already shown.
16-bit fractional numbers use a format similar to that of 8-bit fractional numbers; the high 8 bits have the same format as the
8-bit format. The low 8 bits are only an increase of accuracy of the 8-bit format; while the 8-bit format has an accuracy of
±2
-8, the16-bit format has an accuracy of ± 2-16. Then again, the 32-bit fractional numbers are an increase of accuracy to
the 16-bit fractional numbers. Note the important difference between integers and fractional numbers when extra byte(s)
are used to store the number: while the accuracy of the numbers is increased when fractional numbers are used, the range
of numbers that may be represented is extended when integers are used.
As mentioned earlier, using signed fractional numbers in the range [-1, 1> has one main advantage to integers: when mul-
tiplying two numbers in the range [-1, 1>, the result will be in the range [-1, 1], and an approximation (the highest byte(s)) of
the result may be stored in the same number of bytes as the factors, with one exception: when both factors are -1, the prod-
uct should be 1, but since the number 1 cannot be represented using this number format, the FMULS instruction will
instead place the number -1 in R1:R0. The user should therefore assure that at least one of the operands is not -1 when
using the FMULS instruction. The 16-bit x 16-bit fractional multiply also has this restriction.
Example 5 Basic Usage 8-bit x 8-bit = 16-bit Signed Fractional Multiply
This example shows an assembly code that reads the port E input value and multiplies this value with a fractional constant
(-0.625) before storing the result in register pair R17:R16.
in r16,PINE ; Read pin values
ldi r17,$B0 ; Load -0.625 into r17
fmuls r16,r17 ; r1:r0 = r17 * r16
movw r17:r16,r1:r0; Move the result to the r17:r16
; register pair
Note that the usage of the FMULS (and FMUL) instructions is very similar to the usage of the MULS and MUL instructions.
Example 6 Multiply-accumulate Operation
The example below uses data from the ADC. The ADC should be configured so that the format of the ADC result is com-
patible with the fractional twos complement format. For the ATmega83/163, this means that the ADLAR bit in the ADMUX
I/O register is set and a differential channel is used. (The ADC result is normalized to one.)
ldi r23,$62 ; Load highbyte of
; fraction 0.771484375
ldi r22,$C0 ; Load lowbyte of
; fraction 0.771484375
in r20,ADCL ; Get lowbyte of ADC conversion
in r21,ADCH ; Get highbyte of ADC conversion
callfmac16x16_32;Call routine for signed fractional
; multiply accumulate
The registers R19:R18:R17:R16 will be incremented with the result of the multiplication of 0.771484375 with the ADC con-
version result. In this example, the ADC result is treated as a signed fraction number. We could also treat it as a signed
integer and call it mac16x16_32 instead of fmac16x16_32. In this case, the 0.771484375 should be replaced with an
integer.
AT94K Family
93
Implementations
mul16x16_16
Description
Multiply of two 16-bit numbers with a 16-bit result.
Usage
R17:R16 = R23:R22 R21:R20
Statistics
Cycles: 9 + ret
Words: 6 + ret
Register usage: R0, R1 and R16 to R23 (8 registers)(1)
Note: 1. Full orthogonality, i.e., any register pair can be used as long as the result and the two operands do not share register pairs.
The routine is non-destructive to the operands.
mul16x16_16:
mul r22, r20 ; al * bl
movw r17:r16, r1:r0
mul r23, r20 ; ah * bl
add r17, r0
mul r21, r22 ; bh * al
add r17, r0
ret
mul16x16_32
Description
Unsigned multiply of two 16-bit numbers with a 32-bit result.
Usage
R19:R18:R17:R16 = R23:R22 R21:R20
Statistics
Cycles: 17 + ret
Words: 13 + ret
Register usage: R0 to R2 and R16 to R23 (11 registers)(1)
Note: 1. Full orthogonality, i.e., any register pair can be used as long as the result and the two operands do not share register pairs.
The routine is non-destructive to the operands.
mul16x16_32:
clr r2
mul r23, r21 ; ah * bh
movw r19:r18, r1:r0
mul r22, r20 ; al * bl
movw r17:r16, r1:r0
mul r23, r20 ; ah * bl
add r17, r0
adc r18, r1
adc r19, r2
mul r21, r22 ; bh * al
add r17, r0
adc r18, r1
adc r19, r2
ret
AT94K Family
94
muls16x16_32
Description
Signed multiply of two 16-bit numbers with a 32-bit result.
Usage
R19:R18:R17:R16 = R23:R22 R21:R20
Statistics
Cycles: 19 + ret
Words: 15 + ret
Register usage: R0 to R2 and R16 to R23 (11 registers)(1)
Note: 1. The routine is non-destructive to the operands.
muls16x16_32:
clr r2
muls r23, r21; (signed)ah * (signed)bh
movw r19:r18, r1:r0
mul r22, r20; al * bl
movw r17:r16, r1:r0
mulsu r23, r20; (signed)ah * bl
sbc r19, r2 ; Sign extend
add r17, r0
adc r18, r1
adc r19, r2
mulsu r21, r22; (signed)bh * al
sbc r19, r2 ; Sign Extend
add r17, r0
adc r18, r1
adc r19, r2
ret
mac16x16_32
Description
Signed multiply-accumulate of two 16-bit numbers with a 32-bit result.
Usage
R19:R18:R17:R16 += R23:R22 R21:R20
Statistics
Cycles: 23 + ret
Words: 19 + ret
Register usage: R0 to R2 and R16 to R23 (11 registers)
mac16x16_32: ; Register Usage Optimized
clr r2
muls r23, r21 ; (signed)ah * (signed)bh
add r18, r0
adc r19, r1
mul r22, r20 ; al * bl
add r16, r0
adc r17, r1
AT94K Family
95
adc r18, r2
adc r19, r2
mulsu r23, r20 ; (signed)ah * bl
sbc r19, r2
add r17, r0
adc r18, r1
adc r19, r2
mulsu r21, r22 ; (signed)bh * al
sbc r19, r2 ; Sign extend
add r17, r0
adc r18, r1
adc r19, r2
ret
mac16x16_32_method_B: ; uses two temporary registers (r4,r5), Speed / Size Optimized
; but reduces cycles/words by 1
clr r2
muls r23, r21 ; (signed)ah * (signed)bh
movw r5:r4,r1:r0
mul r22, r20 ; al * bl
add r16, r0
adc r17, r1
adc r18, r4
adc r19, r5
mulsu r23, r20 ; (signed)ah * bl
sbc r19, r2 ; Sign extend
add r17, r0
adc r18, r1
adc r19, r2
mulsu r21, r22 ; (signed)bh * al
sbc r19, r2 ; Sign extend
add r17, r0
adc r18, r1
adc r19, r2
ret
AT94K Family
96
fmuls16x16_32
Description
Signed fractional multiply of two 16-bit numbers with a 32-bit result.
Usage
R19:R18:R17:R16 = (R23:R22 R21:R20) << 1
Statistics
Cycles: 20 + ret
Words: 16 + ret
Register usage: R0 to R2 and R16 to R23 (11 registers)
Note: The routine is non-destructive to the operands.
fmuls16x16_32:
clr r2
fmuls r23, r21 ; ( (signed)ah * (signed)bh ) << 1
movw r19:r18, r1:r0
fmul r22, r20 ; ( al * bl ) << 1
adc r18, r2
movw r17:r16, r1:r0
fmulsu r23, r20; ( (signed)ah * bl ) << 1
sbc r19, r2 ; Sign extend
add r17, r0
adc r18, r1
adc r19, r2
fmulsu r21, r22; ( (signed)bh * al ) << 1
sbc r19, r2 ; Sign extend
add r17, r0
adc r18, r1
adc r19, r2
ret
fmac16x16_32
Description
Signed fractional multiply-accumulate of two 16-bit numbers with a 32-bit result.
Usage
R19:R18:R17:R16 += (R23:R22 R21:R20) << 1
Statistics
Cycles: 25 + ret
Words: 21 + ret
Register usage: R0 to R2 and R16 to R23 (11 registers)
fmac16x16_32: ; Register usage optimized
clr r2
fmuls r23, r21 ; ( (signed)ah * (signed)bh ) << 1
add r18, r0
adc r19, r1
fmul r22, r20 ; ( al * bl ) << 1
AT94K Family
97
adc r18, r2
adc r19, r2
add r16, r0
adc r17, r1
adc r18, r2
adc r19, r2
fmulsu r23, r20 ; ( (signed)ah * bl ) << 1
sbc r19, r2
add r17, r0
adc r18, r1
adc r19, r2
fmulsu r21, r22 ; ( (signed)bh * al ) << 1
sbc r19, r2
add r17, r0
adc r18, r1
adc r19, r2
ret
fmac16x16_32_method_B: ; uses two temporary registers (r4,r5), speed / Size optimized
; but reduces cycles/words by 2
clr r2
fmuls r23, r21 ; ( (signed)ah * (signed)bh ) << 1
movw r5:r4,r1:r0
fmul r22, r20 ; ( al * bl ) << 1
adc r4, r2
add r16, r0
adc r17, r1
adc r18, r4
adc r19, r5
fmulsu r23, r20 ; ( (signed)ah * bl ) << 1
sbc r19, r2
add r17, r0
adc r18, r1
adc r19, r2
fmulsu r21, r22 ; ( (signed)bh * al ) << 1
sbc r19, r2
add r17, r0
adc r18, r1
adc r19, r2
ret
Comment on Implementations
All 16-bit x 16-bit = 32-bit functions implemented here start by clearing the R2 register, which is just used as a dummy
register with the add with carry (ADC) and subtract with carry (SBC) operations. These operations do not alter the con-
AT94K Family
98
tents of the R2 register. If the R2 register is not used elsewhere in the code, it is not necessary to clear the R2 register each
time these functions are called, but only once prior to the first call to one of the functions.
AT94K Family
99
UARTs
The FPSLIC features two full duplex (separate receive and transmit registers) Universal Asynchronous Receiver and
Transmitter (UART). The main features are:
Baud-rate Generator Generates any Baud-rate
High Baud-rates at Low XTAL Frequencies
8 or 9 Bits Data
Noise Filtering
Overrun Detection
Framing Error Detection
False Start Bit Detection
Three Separate Interrupts on TX Complete, TX Data Register Empty and RX Complete
Multi-processor Communication Mode
Double Speed UART Mode
Data Transmission
A block schematic of the UART transmitter is shown in Figure 51. The two UARTs are identical and the functionality is
described in general for the two UARTs.
Figure 51. UART Transmitter(1)
Note: 1. n= 0,1
PE0/
PE2
U2Xn
10(11)-BIT TX
SHIFT REGISTER
PIN CONTROL
LOGIC
UART CONTROL AND
STATUS REGISTER
(UCSRnA)
UART CONTROL AND
STATUS REGISTER
(UCSRnB)
CONTROL LOGIC
BAUD RATE
GENERATOR
TXCn
IRQ
UDREn
IRQ
DATA BU S
RXCIEn
TXCIEn
UDRIEn
TXCn
UDREn
RXENn
TXENn
CHR9n
RXB8n
TXB8n
RXCn
TXCn
UDREn
FEn
MPCMPn
ORn
IDLE
BAUD
STORE UDRn
SHIFT ENABLE
DATA BU S
BAUD x 16 /16 UART I/O DATA
REGISTER (UDRn)
XTAL
TXDn
AT94K Family
100
Data transmission is initiated by writing the data to be transmitted to the UART I/O Data Register, UDRn. Data is trans-
ferred from UDRn to the Transmit shift register when:
A new character has been written to UDRn after the stop bit from the previous character has been shifted out. The shift
register is loaded immediately.
A new character has been written to UDRn before the stop bit from the previous character has been shifted out. The shift
register is loaded when the stop bit of the character currently being transmitted has been shifted out.
If the 10(11)-bit Transmitter shift register is empty, data is transferred from UDRn to the shift register. At this time the
UDREn (UART Data Register Empty) bit in the UART Control and Status Register, UCSRnA, is set. When this bit is set
(one), the UART is ready to receive the next character. At the same time as the data is transferred from UDRn to the
10(11)-bit shift register, bit 0 of the shift register is cleared (start bit) and bit 9 or 10 is set (stop bit). If 9-bit data word is
selected (the CHR9n bit in the UART Control and Status Register, UCSRnB is set), the TXB8 bit in UCSRnB is transferred
to bit 9 in the Transmit shift register.
On the Baud-rate clock following the transfer operation to the shift register, the start bit is shifted out on the TXDn pin. Then
follows the data, LSB first. When the stop bit has been shifted out, the shift register is loaded if any new data has been writ-
ten to the UDRn during the transmission. During loading, UDREn is set. If there is no new data in the UDRn register to send
when the stop bit is shifted out, the UDREn flag will remain set until UDRn is written again. When no new data has been
written, and the stop bit has been present on TXDn for one bit length, the TX Complete flag, TXCn, in UCSRnA is set.
The TXENn bit in UCSRnB enables the UART transmitter when set (one). When this bit is cleared (zero), the PE0 (UART0)
or PE2 (UART1) pin can be used for general I/O. When TXENn is set, the UART Transmitter will be connected to PE0
(UART0) or PE2 (UART1), which is forced to be an output pin regardless of the setting of the DDE0 bit in DDRE (UART0)
or DDE2 in DDRE (UART1).
AT94K Family
101
Data Reception
Figure 52 shows a block diagram of the UART Receiver.
Figure 52. UART Receiver(1)
Note: 1. n= 0,1
PE1/
PE3
DATA BU S
BAUD
UART I/O DATA
REGISTER (UDRn)
10(11)-BIT RX
SHIFT REGISTER
STORE UDRn
/16
BAUD x 16
RXENn
TXENn
CHR9n
RXB8n
TXB8n
U2Xn
RXCn
TXCn
UDREn
FEn
MPCMPn
ORn
UART CONTROL AND
STATUS REGISTER
(UCSRnB)
UART CONTROL AND
STATUS REGISTER
(UCSRnA)
RXCIEn
TXCIEn
UDRIEn
RXCn
DATA BU S
PIN CONTROL
LOGIC
BAUD RATE
GENERATOR
XTAL
RXCn
IRQ
DATA RECOVERY
LOGIC
RXDn
AT94K Family
102
The receiver front-end logic samples the signal on the RXDn pin at a frequency 16 times the baud-rate. While the line is
idle, one single sample of logic 0 will be interpreted as the falling edge of a start bit, and the start bit detection sequence is
initiated. Let sample 1 denote the first zero-sample. Following the 1-to-0 transition, the receiver samples the RXDn pin at
samples 8, 9 and 10. If two or more of these three samples are found to be logic 1s, the start bit is rejected as a noise spike
and the receiver starts looking for the next 1-to-0 transition.
If however, a valid start bit is detected, sampling of the data bits following the start bit is performed. These bits are also
sampled at samples 8, 9 and 10. The logical value found in at least two of the three samples is taken as the bit value. All
bits are shifted into the transmitter shift register as they are sampled. Sampling of an incoming character is shown in
Figure 53. Note that the description above is not valid when the UART transmission speed is doubled. See Double Speed
Transmissionon page 107 for a detailed description.
Figure 53. Sampling Received Data(1)
Note: 1. This figure is not valid when the UART speed is doubled. See Double Speed Transmissionon page 107 for a detailed
description.
When the stop bit enters the receiver, the majority of the three samples must be one to accept the stop bit. If two or more
samples are logic 0s, the Framing Error (FEn) flag in the UART Control and Status Register (UCSRnA) is set. Before read-
ing the UDRn register, the user should always check the FEn bit to detect Framing Errors.
Whether or not a valid stop bit is detected at the end of a character reception cycle, the data is transferred to UDRn and the
RXCn flag in UCSRnA is set. UDRn is in fact two physically separate registers, one for transmitted data and one for
received data. When UDRn is read, the Receive Data register is accessed, and when UDRn is written, the Transmit Data
register is accessed. If 9 bit data word is selected (the CHR9n bit in the UART Control and Status Register, UCSRnB is
set), the RXB8n bit in UCSRnB is loaded with bit 9 in the Transmit shift register when data is transferred to UDRn.
If, after having received a character, the UDRn register has not been read since the last receive, the OverRun (ORn) flag in
UCSRnB is set. This means that the last data byte shifted into to the shift register could not be transferred to UDRn and has
been lost. The ORn bit is buffered, and is updated when the valid data byte in UDRn is read. Thus, the user should always
check the ORn bit after reading the UDRn register in order to detect any overruns if the baud-rate is high or CPU load is
high.
When the RXEN bit in the UCSRnB register is cleared (zero), the receiver is disabled. This means that the PE1 (n=0) or
PE3 (n=1) pin can be used as a general I/O pin. When RXENn is set, the UART Receiver will be connected to PE1
(UART0) or PE3 (UART1), which is forced to be an input pin regardless of the setting of the DDE1 in DDRE (UART0) or
DDB2 bit in DDRB (UART1). When PE1 (UART0) or PE3 (UART1) is forced to input by the UART, the PORTE1 (UART0)
or PORTE3 (UART1) bit can still be used to control the pull-up resistor on the pin.
When the CHR9n bit in the UCSRnB register is set, transmitted and received characters are 9 bits long plus start and stop
bits. The 9th data bit to be transmitted is the TXB8n bit in UCSRnB register. This bit must be set to the wanted value before
a transmission is initiated by writing to the UDRn register. The 9th data bit received is the RXB8n bit in the UCSRnB
register.
Multi-processor Communication Mode
The Multi-processor Communication Mode enables several Slave MCUs to receive data from a Master MCU. This is done
by first decoding an address byte to find out which MCU has been addressed. If a particular Slave MCU has been
addressed, it will receive the following data bytes as normal, while the other Slave MCUs will ignore the data bytes until
another address byte is received.
For an MCU to act as a Master MCU, it should enter 9-bit transmission mode (CHR9n in UCSRnB set). The 9-bit must be
one to indicate that an address byte is being transmitted, and zero to indicate that a data byte is being transmitted.
AT94K Family
103
For the Slave MCUs, the mechanism appears slightly different for 8-bit and 9-bit Reception mode. In 8-bit Reception mode
(CHR9n in UCSRnB cleared), the stop bit is one for an address byte and zero for a data byte. In 9-bit Reception mode
(CHR9n in UCSRnB set), the 9-bit is one for an address byte and zero for a data byte, whereas the stop bit is always high.
The following procedure should be used to exchange data in Multi-processor Communication mode:
1. All Slave MCUs are in Multi-processor Communication Mode (MPCMn in UCSRnA is set).
2. The Master MCU sends an address byte, and all Slaves receive and read this byte. In the Slave MCUs, the
RXCn flag in UCSRnA will be set as normal.
3. Each Slave MCU reads the UDRn register and determines if it has been selected. If so, it clears the MPCMn bit
in UCSRnA, otherwise it waits for the next address byte.
4. For each received data byte, the receiving MCU will set the receive complete flag (RXCn in UCSRnA. In 8-bit
mode, the receiving MCU will also generate a framing error (FEn in UCSRnA set), since the stop bit is zero. The
other Slave MCUs, which still have the MPCMn bit set, will ignore the data byte. In this case, the UDRn register
and the RXCn, FEn, or flags will not be affected.
5. After the last byte has been transferred, the process repeats from step 2.
UART Control
UART0 I/O Data Register UDR0
UART1 I/O Data Register UDR1
The UDRn register is actually two physically separate registers sharing the same I/O address. When writing to the register,
the UART Transmit Data register is written. When reading from UDRn, the UART Receive Data register is read.
UART0 Control and Status Registers UCSR0A
UART1 Control and Status Registers UCSR1A
Bit 7 - RXC0/RXC1: UART Receive Complete
This bit is set (one) when a received character is transferred from the Receiver Shift register to UDRn. The bit is set regard-
less of any detected framing errors. When the RXCIEn bit in UCSRnB is set, the UART Receive Complete interrupt will be
executed when RXCn is set (one). RXCn is cleared by reading UDRn. When interrupt-driven data reception is used, the
Bit 76543210
$0C ($2C) MSB LSB UDR0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$03 ($23) MSB LSB UDR1
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$0B ($2B) RXC0 TXC0 UDRE0 FE0 OR0 - U2X0 MPCM0 UCSR0A
Read/Write R R/W R R R R R/W R/W
Initial Value 0 0 1 0 0 0 0 0
Bit 76543210
$02 ($22) RXC1 TXC1 UDRE1 FE1 OR1 - U2X1 MPCM1 UCSR1A
Read/Write R R/W R R R R R/W R/W
Initial Value 0 0 1 0 0 0 0 0
AT94K Family
104
UART Receive Complete Interrupt routine must read UDRn in order to clear RXCn, otherwise a new interrupt will occur
once the interrupt routine terminates.
Bit 6 - TXC0/TXC1: UART Transmit Complete
This bit is set (one) when the entire character (including the stop bit) in the Transmit Shift register has been shifted out and
no new data has been written to UDRn. This flag is especially useful in half-duplex communications interfaces, where a
transmitting application must enter receive mode and free the communications bus immediately after completing the
transmission.
When the TXCIEn bit in UCSRnB is set, setting of TXCn causes the UART Transmit Complete interrupt to be executed.
TXCn is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, the TXCn bit is
cleared (zero) by writing a logic 1 to the bit.
Bit 5 - UDRE0/UDRE1: UART Data Register Empty
This bit is set (one) when a character written to UDRn is transferred to the Transmit shift register. Setting of this bit indi-
cates that the transmitter is ready to receive a new character for transmission.
When the UDRIEn bit in UCSRnB is set, the UART Transmit Complete interrupt will be executed as long as UDREn is set
and the global interrupt enable bit in SREG is set. UDREn is cleared by writing UDRn. When interrupt-driven data transmit-
tal is used, the UART Data Register Empty Interrupt routine must write UDRn in order to clear UDREn, otherwise a new
interrupt will occur once the interrupt routine terminates.
UDREn is set (one) during reset to indicate that the transmitter is ready.
Bit 4 - FE0/FE1: Framing Error
This bit is set if a Framing Error condition is detected, i.e., when the stop bit of an incoming character is zero.
The FEn bit is cleared when the stop bit of received data is one.
Bit 3 - OR0/OR1: OverRun
This bit is set if an Overrun condition is detected, i.e., when a character already present in the UDRn register is not read
before the next character has been shifted into the Receiver Shift register. The ORn bit is buffered, which means that it will
be set once the valid data still in UDRn is read.
The ORn bit is cleared (zero) when data is received and transferred to UDRn.
Bit 2 - Res: Reserved Bit
This bit is reserved bit in the FPSLIC and will always read as zero.
Bits 1 - U2X0/U2X1: Double the UART Transmission Speed
When this bit is set (one) the UART speed will be doubled. This means that a bit will be transmitted/received in eight CPU
clock periods instead of 16 CPU clock periods. For a detailed description, see Double Speed Transmissionon page 107.
Bit 0 - MPCM0/MPCM1: Multi-processor Communication Mode
This bit is used to enter Multi-processor Communication Mode. The bit is set when the Slave MCU waits for an address
byte to be received. When the MCU has been addressed, the MCU switches off the MPCMn bit, and starts data reception.
For a detailed description, see Multi-processor Communication Mode.
AT94K Family
105
UART0 Control and Status Registers UCSR0B
UART1 Control and Status Registers UCSR1B
Bit 7 - RXCIE0/RXCIE1: RX Complete Interrupt Enable
When this bit is set (one), a setting of the RXCn bit in UCSRnA will cause the Receive Complete interrupt routine to be
executed provided that global interrupts are enabled.
Bit 6 - TXCIE0/TXCIE1: TX Complete Interrupt Enable
When this bit is set (one), a setting of the TXCn bit in UCSRnA will cause the Transmit Complete interrupt routine to be
executed provided that global interrupts are enabled.
Bit 5 - UDRIE0/UDREI1: UART Data Register Empty Interrupt Enable
When this bit is set (one), a setting of the UDREn bit in UCSRnA will cause the UART Data Register Empty interrupt routine
to be executed provided that global interrupts are enabled.
Bit 4 - RXEN0/RXEN1: Receiver Enable
This bit enables the UART receiver when set (one). When the receiver is disabled, the TXCn, ORn and FEn status flags
cannot become set. If these flags are set, turning off RXENn does not cause them to be cleared.
Bit 3 - TXEN0/TXEN1: Transmitter Enable
This bit enables the UART transmitter when set (one). When disabling the transmitter while transmitting a character, the
transmitter is not disabled before the character in the shift register plus any following character in UDRn has been com-
pletely transmitted.
Bit 2 - CHR90/CHR91: 9-bit Characters
When this bit is set (one) transmitted and received characters are 9-bit long plus start and stop bits. The 9-bit is read and
written by using the RXB8n and TXB8n bits in UCSRnB, respectively. The 9th data bit can be used as an extra stop bit or a
parity bit.
Bit 1 - RXB80/RXB81: Receive Data Bit 8
When CHR9n is set (one), RXB8n is the 9th data bit of the received character.
Bit 0 - TXB80/TXB81: Transmit Data Bit 8
When CHR9n is set (one), TXB8n is the 9th data bit in the character to be transmitted.
Bit 76543210
$0A ($2A) RXCIE0 TXCIE0 UDRIE0 RXEN0 TXEN0 CHR90 RXB80 TXB80 UCSR0B
Read/Write R/W R/W R/W R/W R/W R/W R R/W
Initial Value 0 0 0 0 0 0 1 0
Bit 76543210
$01 ($21) RXCIE1 TXCIE1 UDRIE1 RXEN1 TXEN1 CHR91 RXB81 TXB81 UCSR1B
Read/Write R/W R/W R/W R/W R/W R/W R R/W
Initial Value 0 0 0 0 0 0 1 0
AT94K Family
106
Baud-rate Generator
The baud-rate generator is a frequency divider which generates baud-rates according to the following equation:
BAUD = Baud-rate
fCK= Crystal Clock frequency
UBR = Contents of the UBRRHI and UBRRn registers, (0 - 4095)
Note that this equation is not valid when the UART transmission speed is doubled. See Double Speed Transmissionon
page 107 for a detailed description.
For standard crystal frequencies, the most commonly used baud-rates can be generated by using the UBR settings in
Table 29. UBR values which yield an actual baud-rate differing less than 2% from the target baud-rate, are bold in the table.
However, using baud-rates that have more than 1% error is not recommended. High error ratings give less noise
resistance.
Table 29. UBR Settings at Various Crystal Frequencies
BAUD fCK
16(UBR 1 )+
----------------------------------=
Clock
MHz
UBRRHI
7:4 or
3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Error
Clock
MHz
UBRRHI
7:4 or
3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Error
10000 00011001 019 25 2404 2400 0.2 1.843 0000 00101111 02F 47 2400 2400 0.0
0000 00001100 00C 12 4808 4800 0.2 0000 00010111 017 23 4800 4800 0.0
0000 00000110 006 6 8929 9600 7.5 0000 00001011 00B 11 9600 9600 0.0
0000 00000011 003 3 15625 14400 7.8 0000 00000111 007 7 14400 14400 0.0
0000 00000010 002 2 20833 19200 7.8 0000 00000101 005 5 19200 19200 0.0
0000 00000001 001 1 31250 28880 7.6 0000 00000011 003 3 28800 28880 0.3
0000 00000001 001 1 31250 38400 22.9 0000 00000010 002 2 38400 38400 0.0
0000 00000000 000 0 62500 57600 7.8 0000 00000001 001 1 57600 57600 0.0
0000 00000000 000 0 62500 76800 22.9 0000 00000001 001 1 57600 76800 33.3
0000 00000000 000 0 62500 115200 84.3 0000 00000000 000 0 115200 115200 0.0
Clock
MHz
UBRRHI
7:4 or
3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Error
Clock
MHz
UBRRHI
7:4 or
3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Error
9.216 0000 11101111 0EF 239 2400 2400 0.0 18.43 0001 11011111 1DF 479 2400 2400 0.0
0000 01110111 077 119 4800 4800 0.0 0000 11101111 0EF 239 4800 4800 0.0
0000 00111011 03B 59 9600 9600 0.0 0000 01110111 077 119 9600 9600 0.0
0000 00100111 027 39 14400 14400 0.0 0000 01001111 04F 79 14400 14400 0.0
0000 00011101 01D 29 19200 19200 0.0 0000 00111011 03B 59 19200 19200 0.0
0000 00010011 013 19 28800 28880 0.3 0000 00100111 027 39 28800 28880 0.3
0000 00001110 00E 14 38400 38400 0.0 0000 00011101 01D 29 38400 38400 0.0
0000 00001001 009 9 57600 57600 0.0 0000 00010011 013 19 57600 57600 0.0
0000 00000111 007 7 72000 76800 6.7 0000 00001110 00E 14 76800 76800 0.0
0000 00000100 004 4 115200 115200 0.0 0000 00001001 009 9 115200 115200 0.0
0000 00000001 001 1 288000 230400 20.0 0000 00000100 004 4 230400 230400 0.0
0000 00000000 000 0 576000 460800 20.0 0000 00000001 001 1 576000 460800 20.0
0000 00000000 000 0 576000 912600 58.4 0000 00000000 000 0 1152000 912600 20.8
Clock
MHz
UBRRHI
7:4 or
3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Error
Clock
MHz
UBRRHI
7:4 or
3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Error
#### 0010 10011001 299 665 2400 2400 0.0 40 0100 00010001 411 1041 2399 2400 0.0
0001 01001100 14C 332 4800 4800 0.0 0010 00001000 208 520 4798 4800 0.0
0000 10100110 0A6 166 9572 9600 0.3 0001 00000011 103 259 9615 9600 0.2
0000 01101110 06E 110 14401 14400 0.0 0000 10101100 0AC 172 14451 14400 0.4
0000 01010010 052 82 19259 19200 0.3 0000 10000001 081 129 19231 19200 0.2
0000 00110110 036 54 29064 28880 0.6 0000 01010110 056 86 28736 28880 0.5
0000 00101001 029 41 38060 38400 0.9 0000 01000000 040 64 38462 38400 0.2
0000 00011011 01B 27 57089 57600 0.9 0000 00101010 02A 42 58140 57600 0.9
0000 00010100 014 20 76119 76800 0.9 0000 00100000 020 32 75758 76800 1.4
0000 00001101 00D 13 114179 115200 0.9 0000 00010101 015 21 113636 115200 1.4
0000 00000110 006 6 228357 230400 0.9 0000 00001010 00A 10 227273 230400 1.4
0000 00000011 003 3 399625 460800 15.3 0000 00000100 004 4 500000 460800 7.8
0000 00000001 001 1 799250 912600 14.2 0000 00000010 002 2 833333 912600 9.5
AT94K Family
107
UART0 and UART1 High Byte Baud-rate Register UBRRHI
The UART baud register is a 12-bit register. The 4 most significant bits are located in a separate register, UBRRHI. Note
that both UART0 and UART1 share this register. Bit 7 to bit 4 of UBRRHI contain the 4 most significant bits of the UART1
baud register. Bit 3 to bit 0 contain the 4 most significant bits of the UART0 baud register.
UART0 Baud-rate Register Low Byte UBRR0
UART1 Baud-rate Register Low Byte UBRR1
UBRRn stores the 8 least significant bits of the UART baud-rate register.
Double Speed Transmission
The FPSLIC provides a separate UART mode that allows the user to double the communication speed. By setting the U2X
bit in UART Control and Status Register UCSRnA, the UART speed will be doubled. The data reception will differ slightly
from normal mode. Since the speed is doubled, the receiver front-end logic samples the signals on RXDn pin at a fre-
quency 8 times the baud-rate. While the line is idle, one single sample of logic 0 will be interpreted as the falling edge of a
start bit, and the start bit detection sequence is initiated. Let sample 1 denote the first zero-sample. Following the 1-to-0
transition, the receiver samples the RXDn pin at samples 4, 5 and 6. If two or more of these three samples are found to be
logic 1s, the start bit is rejected as a noise spike and the receiver starts looking for the next 1-to-0 transition.
If however, a valid start bit is detected, sampling of the data bits following the start bit is performed. These bits are also
sampled at samples 4, 5 and 6. The logical value found in at least two of the three samples is taken as the bit value. All bits
are shifted into the transmitter shift register as they are sampled. Sampling of an incoming character is shown in Figure 54.
Figure 54. Sampling Received Data when the Transmission Speed is Doubled
Bit 76543210
$20 ($40) MSB1 LSB1 MSB0 LSB0 UBRRHI
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$09 ($29) MSB LSB UBRR0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$00 ($20) MSB LSB UBRR1
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
START BIT D0 D1 D2 D3 D4 D5 D6 D7 STOP BIT
RXD
RECEIVER
SAMPLING
AT94K Family
108
The Baud-rate Generator in Double UART Speed Mode
Note that the baud-rate equation is different from the equation at page 106 when the UART speed is doubled:
BAUD = Baud-rate
fCK= Crystal Clock frequency
UBR = Contents of the UBRRHI and UBRRn registers, (0 - 4095)
Note that this equation is only valid when the UART transmission speed is doubled.
For standard crystal frequencies, the most commonly used baud-rates can be generated by using the UBR settings in
Table 29. UBR values which yield an actual baud-rate differing less than 1.5% from the target baud-rate, are bold in the
table. However since the number of samples are reduced and the system clock might have some variance (this applies
especially when using resonators), it is recommended that the baud-rate error is less than 0.5%.
BAUD fCK
8(UBR 1 )+
------------------------------=
AT94K Family
109
Table 30. UBR Settings at Various Crystal Frequencies in Double Speed Mode
Clock
MHz
UBRRHI
7:4 or 3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Er r o r
Cloc k
MHz
UBRRHI
7:4 or 3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Er r o r
10000 00110011 033 51 2404 2400 0.2 1.843 0000 01011111 05F 95 2400 2400 0.0
0000 00011001 019 25 4808 4800 0.2 0000 00101111 02F 47 4800 4800 0.0
0000 00001100 00C 12 9615 9600 0.2 0000 00010111 017 23 9600 9600 0.0
0000 00001000 008 8 13889 14400 3.7 0000 00001111 00F 15 14400 14400 0.0
0000 00000110 006 6 17857 19200 7.5 0000 00001011 00B 11 19200 19200 0.0
0000 00000011 003 3 31250 28880 7.6 0000 00000111 007 7 28800 28880 0.3
0000 00000010 002 2 41667 38400 7.8 0000 00000101 005 5 38400 38400 0.0
0000 00000001 001 1 62500 57600 7.8 0000 00000011 003 3 57600 57600 0.0
0000 00000001 001 1 62500 76800 22.9 0000 00000010 002 2 76800 76800 0.0
0000 00000000 000 0 125000 115200 7.8 0000 00000001 001 1 115200 115200 0.0
Clock
MHz
UBRRHI
7:4 or 3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Er r o r
Cloc k
MHz
UBRRHI
7:4 or 3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Er r o r
9.216 0001 11011111 1DF 479 2400 2400 0.0 18.43 0011 10111111 3BF 959 2400 2400 0.0
0000 11101111 0EF 239 4800 4800 0.0 0001 11011111 1DF 479 4800 4800 0.0
0000 01110111 077 119 9600 9600 0.0 0000 11101111 0EF 239 9600 9600 0.0
0000 01001111 04F 79 14400 14400 0.0 0000 10011111 09F 159 14400 14400 0.0
0000 00111011 03B 59 19200 19200 0.0 0000 01110111 077 119 19200 19200 0.0
0000 00100111 027 39 28800 28880 0.3 0000 01001111 04F 79 28800 28880 0.3
0000 00011101 01D 29 38400 38400 0.0 0000 00111011 03B 59 38400 38400 0.0
0000 00010011 013 19 57600 57600 0.0 0000 00100111 027 39 57600 57600 0.0
0000 00001110 00E 14 76800 76800 0.0 0000 00011101 01D 29 76800 76800 0.0
0000 00001001 009 9 115200 115200 0.0 0000 00010011 013 19 115200 115200 0.0
0000 00000100 004 4 230400 230400 0.0 0000 00001001 009 9 230400 230400 0.0
0000 00000010 002 2 384000 460800 20.0 0000 00000100 004 4 460800 460800 0.0
0000 00000000 000 0 1152000 912600 20.8 0000 00000010 002 2 768000 912600 18.8
Clock
MHz
UBRRHI
7:4 or 3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Er r o r
Cloc k
MHz
UBRRHI
7:4 or 3:0 UBRRn
UBR
HEX UBR
Actual
Freq
Desired
Freq.
%
Er r o r
25.576 0101 00110011 533 1331 2400 2400 0.0 40 1000 00100010 822 2082 2400 2400 0.0
0010 10011001 299 665 4800 4800 0.0 0100 00010001 411 1041 4798 4800 0.0
0001 01001110 14E 334 9543 9600 0.6 0010 00001000 208 520 9597 9600 0.0
0000 11011101 0DD 221 14401 14400 0.0 0001 01011010 15A 346 14409 14400 0.1
0000 10100110 0A6 166 19144 19200 0.3 0001 00000011 103 259 19231 19200 0.2
0000 01101110 06E 110 28802 28880 0.3 0000 10101100 0AC 172 28902 28880 0.1
0000 01010010 052 82 38518 38400 0.3 0000 10000001 081 129 38462 38400 0.2
0000 00110111 037 55 57089 57600 0.9 0000 01010110 056 86 57471 57600 0.2
0000 00101001 029 41 76119 76800 0.9 0000 01000000 040 64 76923 76800 0.2
0000 00011011 01B 27 114179 115200 0.9 0000 00101010 02A 42 116279 115200 0.9
0000 00001101 00D 13 228357 230400 0.9 0000 00010101 015 21 227273 230400 1.4
0000 00000110 006 6 456714 460800 0.9 0000 00001010 00A 10 454545 460800 1.4
0000 00000011 003 3 799250 912600 14.2 0000 00000100 004 4 1000000 912600 8.7
AT94K Family
110
2-wire Serial Interface (Byte Oriented)
The 2-wire Serial Bus is a bi-directional two-wire serial communication standard. It is designed primarily for simple but effi-
cient integrated circuit (IC) control. The system is comprised of two lines, SCL (Serial Clock) and SDA (Serial Data) that
carry information between the ICs connected to them. Various communication configurations can be designed using this
bus. Figure 55 shows a typical 2-wire Serial Bus configuration. Any device connected to the bus can be Master or Slave.
Figure 55. 2-wire Serial Bus Configuration
The 2-wire Serial Interface provides a serial interface that meets the 2-wire Serial Bus specification and supports Mas-
ter/Slave and Transmitter/Receiver operation at up to 400 kHz bus clock rate. The 2-wire Serial Interface has hardware
support for the 7-bit addressing, but is easily extended to 10-bit addressing format in software. When operating in 2-wire
Serial mode, i.e., when TWEN is set, a glitch filter is enabled for the input signals from the pins SCL and SDA, and the out-
put from these pins are slew-rate controlled. The 2-wire Serial Interface is byte oriented. The operation of the serial 2-wire
Serial Bus is shown as a pulse diagram in Figure 56, including the START and STOP conditions and generation of ACK
signal by the bus receiver.
Figure 56. 2-wire Serial Bus Timing Diagram
The block diagram of the 2-wire Serial Bus interface is shown in Figure 57.
Device 1 Device 2 Device 3 Device n.......
VCC
R1 R2
SCL
SDA
SDA
SCL
MSB R/W
BIT
STOP CONDITION
START
CONDITION REPEATED START CONDITION
12 789 12 89
ACK ACK
ACKNOWLEDGE
FROM RECEIVER
AT94K Family
111
Figure 57. Block diagram of the 2-wire Serial Bus Interface
The CPU interfaces with the 2-wire Serial Interface via the following five I/O registers: the 2-wire Serial Bit Rate Register
(TWBR), the 2-wire Serial Control Register (TWCR), the 2-wire Serial Status Register (TWSR), the 2-wire Serial Data Reg-
ister (TWDR), and the 2-wire Serial Address Register (TWAR, used in Slave mode).
The 2-wire Serial Bit Rate Register TWBR
Bits 7..0 - 2-wire Serial Bit Rate Register
TWBR selects the division factor for the bit rate generator. The bit rate generator is a frequency divider which generates the
SCL clock frequency in the Master modes according to the following equation:
Bit Rate = SCL frequency
fCK = CPU Clock frequency
Bit 76543210
$1C ($3C) TWBR7 TWBR6 TWBR5 TWBR4 TWBR3 TWBR2 TWBR1 TWBR0 TWBR
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
ACK
INPUT
OUTPUT
INPUT
OUTPUT
START/STOP
AND SYNC
ARBITRATION
TIMING
AND
CONTROL
SERIAL CLOCK
GENERATOR
STATE MACHINE
AND
STATUS DECODER
DATA SHIFT
REGISTER
ADDRESS REGISTER
AND
COMPARATOR
TWAR
SDA
SCL
TWDR
CONTROL
REGISTER
STAT US
REGISTER
STAT US
TWCR
TWSR
AVR 8-BIT DATA BUS
AT94K Family
112
TWBR = Contents of the 2-wire Serial Bit Rate Register
Both the receiver and the transmitter can stretch the low period of the SCL line when waiting for user response, thereby
reducing the average bit rate.
The 2-wire Serial Control Register TWCR
Bit 7 - TWINT: 2-wire Serial Interrupt Flag
This bit is set by hardware when the 2-wire Serial Interface has finished its current job and expects application software
response. If the I-bit in the SREG and TWIE in the TWCR register are set (one), the MCU will jump to the interrupt vector at
address $0046. While the TWINT flag is set, the bus SCL clock line low period is stretched. The TWINT flag must be
cleared by software by writing a logic 1 to it. Note that this flag is not automatically cleared by hardware when executing the
interrupt routine. Also note that clearing this flag starts the operation of the 2-wire Serial Interface, so all accesses to the 2-
wire Serial Address Register TWAR, 2-wire Serial Status Register TWSR, and 2-wire Serial Data Register TWDR
must be complete before clearing this flag.
Bit 6 - TWEA: 2-wire Serial Enable Acknowledge Flag
TWEA flag controls the generation of the acknowledge pulse. If the TWEA bit is set, the ACK pulse is generated on the 2-
wire Serial Bus if the following conditions are met:
1. The devices own Slave address has been detected
2. A general call has been received, while the TWGCE bit in the TWAR is set
3. A data byte has been received in Master Receiver or Slave receiver mode
By setting the TWEA bit low the device can be virtually disconnected from the 2-wire Serial Bus temporarily. Address rec-
ognition can then be resumed by setting the TWEA bit again.
Bit 5 - TWSTA: 2-wire Serial Bus START Condition Flag
The TWSTA flag is set by the CPU when it desires to become a Master on the 2-wire Serial Bus. The 2-wire serial hard-
ware checks if the bus is available, and generates a Start condition on the bus if it is free. However, if the bus is not free,
the 2-wire Serial Interface waits until a STOP condition is detected, and then generates a new Start condition to claim the
bus Master status.
Bit 4 - TWSTO: 2-wire Serial Bus STOP Condition Flag
TWSTO is a stop condition flag. In Master mode setting the TWSTO bit in the control register will generate a STOP condi-
tion on the 2-wire Serial Bus. When the STOP condition is executed on the bus, the TWSTO bit is cleared automatically. In
Slave mode setting the TWSTO bit can be used to recover from an error condition. No stop condition is generated on the
bus then, but the 2-wire Serial Interface returns to a well-defined unaddressed Slave mode.
Bit 76543210
$36 ($56) TWINT TWEA TWSTA TWSTO TWWC TWEN - TWIE TWCR
Read/Write R/W R/W R/W R/W R R/W R R/W
Initial Value 0 0 0 0 0 0 0 0
Bit Rate fCK
16 + 2(TWBR)
--------------------------------------=
AT94K Family
113
Bit 3 - TWWC: 2-wire Serial Write Collision Flag
Set when attempting to write to the 2-wire Serial Data Register TWDR when TWINT is low. This flag is updated at each
attempt to write the TWDR register.
Bit 2 - TWEN: 2-wire Serial Interface Enable Flag
The TWEN bit enables 2-wire serial operation. If this flag is cleared (zero), the bus outputs SDA and SCL are set to high
impedance state, and the input signals are ignored. The interface is activated by setting this flag (one).
Bit 1 - Res: Reserved Bit
This bit is a reserved bit in the AT94K and will always read as zero.
Bit 0 - TWIE: 2-wire Serial Interrupt Enable
When this bit is enabled, and the I-bit in SREG is set, the 2-wire Serial Interrupt will be activated for as long as the TWINT
flag is high.
The TWCR is used to control the operation of the 2-wire Serial Interface. It is used to enable the 2-wire Serial Interface, to
initiate a Master access, to generate a receiver acknowledge, to generate a stop condition, and control halting of the bus
while the data to be written to the bus are written to the TWDR. It also indicates a write collision if data is attempted written
to TWDR while the register is inaccessible.
The 2-wire Serial Status Register TWSR
Bits 7..3 - TWS: 2-wire Serial Status
These 5 bits reflect the status of the 2-wire Serial Logic and the 2-wire Serial Bus.
Bits 2..0 - Res: Reserved Bits
These bits are reserved in AT94K and will always read as zero
The TWSR is read only. It contains a status code which reflects the status of the 2-wire Serial Logic and the 2-wire Serial
Bus. There are 26 possible status codes. When TWSR contains $F8, no relevant state information is available and no 2-
wire Serial Interrupt is requested. A valid status code is available in TWSR one CPU clock cycle after the 2-wire Serial
Interrupt flag (TWINT) is set by hardware and is valid until one CPU clock cycle after TWINT is cleared by software.
Table 34 to Table 38 give the status information for the various modes.
The 2-wire Serial Data Register TWDR
Bits 7..0 - TWD: 2-wire Serial Data Register
These eight bits constitute the next data byte to be transmitted, or the latest data byte received on the 2-wire Serial Bus.
In transmit mode, TWDR contains the next byte to be transmitted. In receive mode, the TWDR contains the last byte
received. It is writable while the 2-wire Serial Interface is not in the process of shifting a byte. This occurs when the 2-wire
Serial Interrupt flag (TWINT) is set by hardware. Note that the data register cannot be initialized by the user before the first
interrupt occurs. The data in TWDR remain stable as long as TWINT is set. While data is shifted out, data on the bus is
simultaneously shifted in. TWDR always contains the last byte present on the bus, except after a wake up from Power-
Bit 76543210
$1D ($3D) TWS7 TWS6 TWS5 TWS4 TWS3 - - - TWSR
Read/WriteRRRRRRRR
Initial Value 1 1 1 1 1 0 0 0
Bit 76543210
$1F ($3F) MSB LSB TWDR
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 1 1 1 1 1 1 1 1
AT94K Family
114
down Mode, or Power-save Mode by the 2-wire Serial Interrupt. For example, in the case of the lost bus arbitration, no data
is lost in the transition from Master-to-Slave. Receiving the ACK flag is controlled by the 2-wire Serial Logic automatically,
the CPU cannot access the ACK bit directly.
The 2-wire Serial (Slave) Address Register TWAR
Bits 7..1 - TWA: 2-wire Serial Slave Address Register
These seven bits constitute the Slave address of the 2-wire Serial Bus interface unit.
Bit 0 - TWGCE: 2-wire Serial General Call Recognition Enable Bit
This bit enables, if set, the recognition of the General Call given over the 2-wire Serial Bus.
The TWAR should be loaded with the 7-bit Slave address (in the seven most significant bits of TWAR) to which the 2-wire
Serial Interface will respond when programmed as a Slave transmitter or receiver, and not needed in the Master modes.
The LSB of TWAR is used to enable recognition of the general call address ($00). There is an associated address compar-
ator that looks for the Slave address (or general call address if enabled) in the received serial address. If a match is found,
an interrupt request is generated.
2-wire Serial Modes
The 2-wire Serial Interface can operate in four different modes:
Master Transmitter
Master Receiver
Slave Receiver
Slave Transmitter
Data transfer in each mode of operation is shown in Figure 58 to Figure 61. These figures contain the following
abbreviations:
S: START condition
R: Read bit (high level at SDA)
W: Write bit (low level at SDA)
A: Acknowledge bit (low level at SDA)
A: Not acknowledge bit (high level at SDA)
Data: 8-bit data byte
P: STOP condition
In Figure 58 to Figure 61, circles are used to indicate that the 2-wire Serial Interrupt flag is set. The numbers in the circles
show the status code held in TWSR. At these points, an interrupt routine must be executed to continue or complete the
2-wire Serial Transfer. The 2-wire Serial Transfer is suspended until the 2-wire Serial Interrupt flag is cleared by software.
The 2-wire Serial Interrupt flag is not automatically cleared by hardware when executing the interrupt routine. Also note that
the 2-wire Serial Interface starts execution as soon as this bit is cleared, so that all access to TWAR, TWDR, and TWSR
must have been completed before clearing this flag.
When the 2-wire Serial Interrupt flag is set, the status code in TWSR is used to determine the appropriate software action.
For each status code, the required software action and details of the following serial transfer are given in Table 34 to
Table 38.
Bit 76543210
$1E ($3E) MSB LSB TWGCE TWAR
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 1 1 1 1 1 1 1 0
AT94K Family
115
Master Transmitter Mode
In the Master Transmitter mode, a number of data bytes are transmitter to a Slave receiver (see Figure 58). Before Master
Transmitter mode can be entered, the TWCR must be initialized as follows:
TWEN must be set to enable the 2-wire Serial Interface, TWSTA and TWSTO must be cleared.
The Master Transmitter mode may now be entered by setting the TWSTA bit. The 2-wire Serial Logic will now test the 2-
wire Serial Bus and generate a START condition as soon as the bus becomes free. When a START condition is transmit-
ted, the 2-wire Serial Interrupt flag (TWINT) is set by hardware, and the status code in TWSR will be $08. TWDR must then
be loaded with the Slave address and the data direction bit (SLA+W). The TWINT flag must then be cleared by software
before the 2-wire Serial Transfer can continue. The TWINT flag is cleared by writing a logic 1 to the flag.
When the Slave address and the direction bit have been transmitted and an acknowledgment bit has been received,
TWINT is set again and a number of status codes in TWSR are possible. Status codes $18, $20, or $38 apply to Master
mode, and status codes $68, $78, or $B0 apply to Slave mode. The appropriate action to be taken for each of these status
codes is detailed in Table 34. The data must be loaded when TWINT is high only. If not, the access will be discarded, and
the Write Collision bit TWWC will be set in the TWCR register. This scheme is repeated until a STOP condition is trans-
mitted by writing a logic 1 to the TWSTO bit in the TWCR register.
After a repeated START condition (state $10) the 2-wire Serial Interface may switch to the Master Receiver mode by load-
ing TWDR with SLA+R.
Master Receiver Mode
In the Master Receiver mode, a number of data bytes are received from a Slave transmitter (see Figure 59). The transfer is
initialized as in the Master Transmitter mode. When the START condition has been transmitted, the TWINT flag is set by
hardware. The software must then load TWDR with the 7-bit Slave address and the data direction bit (SLA+R). The 2-wire
Serial Interrupt flag must then be cleared by software before the 2-wire Serial Transfer can continue.
When the Slave address and the direction bit have been transmitted and an acknowledgment bit has been received,
TWINT is set again and a number of status codes in TWSR are possible. Status codes $40, $48, or $38 apply to Master
mode, and status codes $68, $78, or $B0 apply to Slave mode. The appropriate action to be taken for each of these status
codes is detailed in Table 35. Received data can be read from the TWDR register when the TWINT flag is set high by hard-
ware. This scheme is repeated until a STOP condition is transmitted by writing a logic 1 to the TWSTO bit in the TWCR
register.
After a repeated START condition (state $10), the 2-wire Serial Interface may switch to the Master Transmitter mode by
loading TWDR with SLA+W.
Slave Receiver Mode
In the Slave Receiver mode, a number of data bytes are received from a Master Transmitter (see Figure 60). To initiate the
Slave Receiver mode, TWAR and TWCR must be initialized as follows:
The upper 7 bits are the address to which the 2-wire Serial Interface will respond when addressed by a Master. If the LSB
is set, the 2-wire Serial Interface will respond to the general call address ($00), otherwise it will ignore the general call
address.
Table 31. TWCR: Master Transmitter Mode Initialization
TWCR TWINT TWEA TWSTA TWSTO TWWC TWEN -TWIE
value 0X0 0010 X
Table 32. TWAR: Slave Receiver Mode Initialization
TWAR TWA6 TWA5 TWA4 TWA3 TWA2 TWA1 TWA0 TWGCE
value Devices own Slave address
AT94K Family
116
TWEN must be set to enable the 2-wire Serial Interface. The TWEA bit must be set to enable the acknowledgment of the
devices own Slave address or the general call address. TWSTA and TWSTO must be cleared.
When TWAR and TWCR have been initialized, the 2-wire Serial Interface waits until it is addressed by its own Slave
address (or the general call address if enabled) followed by the data direction bit which must be 0 (write) for the 2-wire
Serial Interface to operate in the Slave Receiver mode. After its own Slave address and the write bit have been received,
the 2-wire Serial Interrupt flag is set and a valid status code can be read from TWSR. The status code is used to determine
the appropriate software action. The appropriate action to be taken for each status code is detailed in Table 36. The Slave
Receiver mode may also be entered if arbitration is lost while the 2-wire Serial Interface is in the Master mode (see states
$68 and $78).
If the TWEA bit is reset during a transfer, the 2-wire Serial Interface will return a Not Acknowledged (1) to SDA after the
next received data byte. While TWEA is reset, the 2-wire Serial Interface does not respond to its own Slave address. How-
ever, the 2-wire Serial Bus is still monitored and address recognition may resume at any time by setting TWEA. This
implies that the TWEA bit may be used to temporarily isolate the 2-wire Serial Interface from the 2-wire serial bus.
In ADC Noise Reduction Mode, Power-down Mode, and Power-save Mode, the clock system to the 2-wire Serial Interface
is turned off. If the Slave Receiver mode is enabled, the interface can still acknowledge a general call and its own Slave
address by using the 2-wire serial bus clock as a clock source. The part will then wake up from sleep and the 2-wire Serial
Interface will hold the SCL clock will low during the wake up and until the TWCINT flag is cleared.
Note that the 2-wire Serial Data Register TWDR does not reflect the last byte present on the bus when waking up from
these Sleep Modes.
Slave Transmitter Mode
In the Slave Transmitter mode, a number of data bytes are transmitted to a Master Receiver (see Figure 61). The transfer
is initialized as in the Slave Receiver mode. When TWAR and TWCR have been initialized, the 2-wire Serial Interface waits
until it is addressed by its own Slave address (or the general call address if enabled) followed by the data direction bit which
must be 1 (read) for the 2-wire Serial Interface to operate in the Slave Transmitter mode. After its own Slave address and
the read bit have been received, the 2-wire Serial Interrupt flag is set and a valid status code can be read from TWSR. The
status code is used to determine the appropriate software action. The appropriate action to be taken for each status code is
detailed in Table 37. The Slave Transmitter mode may also be entered if arbitration is lost while the 2-wire Serial Interface
is in the Master mode (see state $B0).
If the TWEA bit is reset during a transfer, the 2-wire Serial Interface will transmit the last byte of the transfer and enter state
$C0 or state $C8. the 2-wire Serial Interface is switched to the not addressed Slave mode, and will ignore the Master if it
continues the transfer. Thus the Master Receiver receives all 1 as serial data. While TWEA is reset, the 2-wire Serial
Interface does not respond to its own Slave address. However, the 2-wire serial bus is still monitored and address recogni-
tion may resume at any time by setting TWEA. This implies that the TWEA bit may be used to temporarily isolate the 2-wire
Serial Interface from the 2-wire serial bus.
Miscellaneous States
There are two status codes that do not correspond to a defined 2-wire Serial Interface state: Status $F8 and Status $00,
see Table 38.
Status $F8 indicates that no relevant information is available because the 2-wire Serial Interrupt flag (TWINT) is not set yet.
This occurs between other states, and when the 2-wire Serial Interface is not involved in a serial transfer.
Status $00 indicates that a bus error has occurred during a 2-wire serial transfer. A bus error occurs when a START or
STOP condition occurs at an illegal position in the format frame. Examples of such illegal positions are during the serial
transfer of an address byte, a data byte or an acknowledge bit. When a bus error occurs, TWINT is set. To recover from a
bus error, the TWSTO flag must set and TWINT must be cleared by writing a logic 1 to it. This causes the 2-wire Serial
Interface to enter the not addressed Slave mode and to clear the TWSTO flag (no other bits in TWCR are affected). The
SDA and SCL lines are released and no STOP condition is transmitted.
Table 33. TWCR: Slave Receiver Mode Initialization
TWCR TWINT TWEA TWSTA TWSTO TWWC TWEN -TWIE
value 0100010 X
AT94K Family
117
Table 34. Status Codes for Master Transmitter Mode
Status
Code
(TWSR)
Status of the 2-wire
Serial Bus and 2-wire
Serial Hardware
Application Software Response
Next Action Taken by 2-wire
Serial HardwareTo/From TWDR
To TWCR
STA STO TWINT TWEA
$08 A START condition
has been transmitted
Load SLA+W X 0 1 X SLA+W will be transmitted;
ACK or NOT ACK will be received
$10 A repeated START
condition has been
transmitted
Load SLA+W or
Load SLA+R
X
X
0
0
1
1
X
X
SLA+W will be transmitted;
ACK or NOT ACK will be received
SLA+R will be transmitted;
Logic will switch to Master Receiver mode
$18 SLA+W has been
transmitted;
ACK has been
received
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or NOT
ACK will be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO flag
will be reset
$20 SLA+W has been
transmitted;
NOT ACK has been
received
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or NOT
ACK will be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO flag
will be reset
$28 Data byte has been
transmitted;
ACK has been
received
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or NOT
ACK will be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO flag
will be reset
$30 Data byte has been
transmitted;
NOT ACK has been
received
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or NOT
ACK will be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO flag
will be reset
$38 Arbitration lost in
SLA+W or data bytes
No TWDR action or
No TWDR action
0
1
0
0
1
1
X
X
2-wire serial bus will be released and not
addressed Slave mode entered
A START condition will be transmitted when
the bus becomes free
AT94K Family
118
Figure 58. Formats and States in the Master Transmitter Mode
S SLA W A DATA A P
$08 $18 $28
S SLA W
$10
AP
$20
P
$30
A or A
$38
A
Other master
continues
A or A
$38
Other master
continues
R
A
$68
Other master
continues
$78 $B0
To corresponding
states in slave mode
MT
MR
Successfull
transmission
to a slave
receiver
Next transfer
started with a
repeated start
condition
Not acknowledge
received after the
slave address
Not acknowledge
received after a data
byte
Arbitration lost in slave
address or data byte
Arbitration lost and
addressed as slave
DATA A
n
From master to slave
From slave to master
Any number of data bytes
and their associated acknowledge bits
This number (contained in TWSR) corresponds
to a defined state of the 2-wire serial bus
AT94K Family
119
Table 35. Status Codes for Master Receiver Mode
Status
Code
(TWSR)
Status of the 2-wire
Serial Bus and 2-wire
Serial Hardware
Application Software Response
Next Action Taken by 2-wire Serial
HardwareTo/From TWDR
To TWCR
STA STO TWINT TWEA
$08 A START condition has
been transmitted
Load SLA+R X 0 1 X SLA+R will be transmitted
ACK or NOT ACK will be received
$10 A repeated START
condition has been
transmitted
Load SLA+R or
Load SLA+W
X
X
0
0
1
1
X
X
SLA+R will be transmitted
ACK or NOT ACK will be received
SLA+W will be transmitted
Logic will switch to Master Transmitter mode
$38 Arbitration lost in
SLA+R or NOT ACK bit
No TWDR action or
No TWDR action
0
1
0
0
1
1
X
X
2-wire serial bus will be released and not
addressed Slave mode will be entered
A START condition will be transmitted when
the bus becomes free
$40 SLA+R has been
transmitted;
ACK has been received
No TWDR action or
No TWDR action
0
0
0
0
1
1
0
1
Data byte will be received and NOT ACK will
be returned
Data byte will be received and ACK will be
returned
$48 SLA+R has been
transmitted;
NOT ACK has been
received
No TWDR action or
No TWDR action or
No TWDR action
1
0
1
0
1
1
1
1
1
X
X
X
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO flag
will be reset
$50 Data byte has been
received;
ACK has been returned
Read data byte or
Read data byte
0
0
0
0
1
1
0
1
Data byte will be received and NOT ACK will
be returned
Data byte will be received and ACK will be
returned
$58 Data byte has been
received;
NOT ACK has been
returned
Read data byte or
Read data byte or
Read data byte
1
0
1
0
1
1
1
1
1
X
X
X
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO flag
will be reset
AT94K Family
120
Figure 59. Formats and States in the Master Receiver Mode
S SLA R A DATA A
$08 $40 $50
S SLA R
$10
AP
$48
A or A
$38
Other master
continues
$38
Other master
continues
W
A
$68
Other master
continues
$78 $B0
To corresponding
states in slave mode
MR
MT
Successfull
reception
from a slave
receiver
Next transfer
started with a
repeated start
condition
Not acknowledge
received after the
slave address
Arbitration lost in slave
address or data byte
Arbitration lost and
addressed as slave
DATA A
n
From master to slave
From slave to master
Any number of data bytes
and their associated acknowledge bits
This number (contained in TWSR) corresponds
to a defined state of the 2-wire serial bus
PDATA A
$58
A
AT94K Family
121
Table 36. Status Codes for Slave Receiver Mode
Status
Code
(TWSR)
Status of the 2-wire
Serial Bus and 2-wire
Serial Hardware
Application Software Response
Next Action Taken by 2-wire
Serial HardwareTo/From TWDR
To TWCR
STA STO TWINT TWEA
$60 Own SLA+W has been
received;
ACK has been returned
No TWDR action or
No TWDR action
X
X
0
0
1
1
0
1
Data byte will be received and NOT ACK
will be returned
Data byte will be received and ACK will be
returned
$68 Arbitration lost in
SLA+R/W as Master;
own SLA+W has been
received;
ACK has been returned
No TWDR action or
No TWDR action
X
X
0
0
1
1
0
1
Data byte will be received and NOT ACK
will be returned
Data byte will be received and ACK will be
returned
$70 General call address
has been received;
ACK has been returned
No TWDR action or
No TWDR action
X
X
0
0
1
1
0
1
Data byte will be received and NOT ACK
will be returned
Data byte will be received and ACK will be
returned
$78 Arbitration lost in
SLA+R/W as Master;
General call address
has been received;
ACK has been returned
No TWDR action or
No TWDR action
X
X
0
0
1
1
0
1
Data byte will be received and NOT ACK
will be returned
Data byte will be received and ACK will be
returned
$80 Previously addressed
with own SLA+W; data
has been received;
ACK has been returned
No TWDR action or
No TWDR action
X
X
0
0
1
1
0
1
Data byte will be received and NOT ACK
will be returned
Data byte will be received and ACK will be
returned
$88 Previously addressed
with own SLA+W; data
has been received;
NOT ACK has been
returned
Read data byte or
Read data byte or
Read data byte or
Read data byte
0
0
1
1
0
0
0
0
1
1
1
1
0
1
0
1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA
Switched to the not addressed Slave mode;
own SLA will be recognized; GCA will be
recognized if GC = 1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA; a
START condition will be transmitted when
the bus becomes free
Switched to the not addressed Slave mode;
own SLA will be recognized; GCA will be
recognized if GC = 1; a START condition
will be transmitted when the bus becomes
free
AT94K Family
122
$90 Previously addressed
with general call; data
has been received;
ACK has been returned
Read data byte or
Read data byte
X
X
0
0
1
1
0
1
Data byte will be received and NOT ACK
will be returned
Data byte will be received and ACK will be
returned
$98 Previously addressed
with general call; data
has been received;
NOT ACK has been
returned
Read data byte or
Read data byte or
Read data byte or
Read data byte
0
0
1
1
0
0
0
0
1
1
1
1
0
1
0
1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA
Switched to the not addressed Slave mode;
own SLA will be recognized; GCA will be
recognized if GC = 1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA; a
START condition will be transmitted when
the bus becomes free
Switched to the not addressed Slave mode;
own SLA will be recognized; GCA will be
recognized if GC = 1; a START condition
will be transmitted when the bus becomes
free
$A0 A STOP condition or
repeated START
condition has been
received while still
addressed as Slave
Read data byte or
Read data byte or
Read data byte or
Read data byte
0
0
1
1
0
0
0
0
1
1
1
1
0
1
0
1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA
Switched to the not addressed Slave mode;
own SLA will be recognized; GCA will be
recognized if GC = 1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA; a
START condition will be transmitted when
the bus becomes free
Switched to the not addressed Slave mode;
own SLA will be recognized; GCA will be
recognized if GC = 1; a START condition
will be transmitted when the bus becomes
free
Table 36. Status Codes for Slave Receiver Mode (Continued)
Status
Code
(TWSR)
Status of the 2-wire
Serial Bus and 2-wire
Serial Hardware
Application Software Response
Next Action Taken by 2-wire
Serial HardwareTo/From TWDR
To TWCR
STA STO TWINT TWEA
AT94K Family
123
Figure 60. Formats and States in the Slave Receiver Mode
S SLA W A DATA A
$60 $80
$88
A
$68
Reception of the own
slave address and one or
more data bytes. All are
acknowledged
Last data byte received
is not acknowledged
Arbitration lost as master
and addressed as slave
Reception of the general call
address and one or more data
bytes
Last data byte received is
not acknowledged
n
From master to slave
From slave to master
Any number of data bytes
and their associated acknowledge bits
This number (contained in TWSR) corresponds
to a defined state of the 2-wire serial bus
P or SDATA A
$80 $A0
P or SA
A DATA A
$70 $90
$98
A
$78
P or SDATA A
$90 $A0
P or SA
General Call
Arbitration lost as master and
addressed as slave by general call
DATA A
AT94K Family
124
Table 37. Status Codes for Slave Transmitter Mode
Status
Code
(TWSR)
Status of the 2-wire
Serial Bus and 2-wire
Serial Hardware
Application Software Response
Next Action Taken by 2-wire
Serial HardwareTo/From TWDR
To TWCR
STA STO TWINT TWEA
$A8 Own SLA+R has been
received;
ACK has been returned
Load data byte or
Load data byte
X
X
0
0
1
1
0
1
Last data byte will be transmitted and NOT
ACK should be received
Data byte will be transmitted and ACK
should be received
$B0 Arbitration lost in
SLA+R/W as Master;
own SLA+R has been
received;
ACK has been returned
Load data byte or
Load data byte
X
X
0
0
1
1
0
1
Last data byte will be transmitted and NOT
ACK should be received
Data byte will be transmitted and ACK
should be received
$B8 Data byte in TWDR has
been transmitted;
ACK has been received
Load data byte or
Load data byte
X
X
0
0
1
1
0
1
Last data byte will be transmitted and NOT
ACK should be received
Data byte will be transmitted and ACK
should be received
$C0 Data byte in TWDR has
been transmitted;
NOT ACK has been
received
No TWDR action or
No TWDR action or
No TWDR action or
No TWDR action
0
0
1
1
0
0
0
0
1
1
1
1
0
1
0
1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA
Switched to the not addressed Slave mode;
own SLA will be recognized; GCA will be
recognized if GC = 1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA; a START
condition will be transmitted when the bus
becomes free
Switched to the not addressed Slave mode;
own SLA will be recognized; GCA will be
recognized if GC = 1; a START condition
will be transmitted when the bus becomes
free
$C8 Last data byte in
TWDR has been
transmitted (TWAE =
0);
ACK has been received
No TWDR action or
No TWDR action or
No TWDR action or
No TWDR action
0
0
1
1
0
0
0
0
1
1
1
1
0
1
0
1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA
Switched to the not addressed Slave mode;
own SLA will be recognized; GCA will be
recognized if GC = 1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA; a START
condition will be transmitted when the bus
becomes free
Switched to the not addressed Slave mode;
own SLA will be recognized; GCA will be
recognized if GC = 1; a START condition
will be transmitted when the bus becomes
free
AT94K Family
125
Figure 61. Formats and States in the Slave Transmitter Mode
Table 38. Status Codes for Miscellaneous States
Status
Code
(TWSR)
Status of the 2-wire
Serial Bus and 2-wire
Serial Hardware
Application Software Response
Next Action Taken by 2-wire
Serial HardwareTo/From TWDR
To TWCR
STA STO TWINT TWEA
$F8 No relevant state
information available;
TWINT = 0
No TWDR action No TWCR action Wait or proceed current transfer
$00 Bus error due to an
illegal START or STOP
condition
No TWDR action 0 1 1 X Only the internal hardware is affected; no
STOP condition is sent on the bus. In all
cases, the bus is released and TWSTO is
cleared.
S SLA R A DATA A
$A8 $B8
A
$B0
Reception of the own
slave address and one or
more data bytes
Last data byte transmitted.
Arbitration lost as master
and addressed as slave
n
From master to slave
From slave to master
Any number of data bytes
and their associated acknowledge bits
This number (contained in TWSR) corresponds
to a defined state of the 2-wire serial bus
P or SDATA
$C0
DATA A
A
$C8
P or SAll 1's
A
AT94K Family
126
I/O Ports
All AVR ports have true read-modify-write functionality when used as general I/O ports. This means that the direction of
one port pin can be changed without unintentionally changing the direction of any other pin with the SBI and CBI instruc-
tions. The same applies for changing drive value (if configured as output) or enabling/disabling of pull-up resistors (if
configured as input).
PortD
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors.
Three I/O memory address locations are allocated for the PortD, one each for the Data Register PORTD, $12($32), Data
Direction Register DDRD, $11($31) and the Port D Input Pins PIND, $10($30). The Port D Input Pins address is read
only, while the Data Register and the Data Direction Register are read/write.
The PortD output buffers can sink 20 mA. As inputs, PortD pins that are externally pulled low will source current if the
pull-up resistors are activated.
PortD Data Register PORTD
PortD Data Direction Register DDRD
PortD Input Pins Address PIND
The PortD Input Pins address PIND is not a register, and this address enables access to the physical value on each
PortD pin. When reading PORTD, the PortD Data Latch is read, and when reading PIND, the logical values present on the
pins are read.
PortD as General Digital I/O
PDn, General I/O pin: The DDDn bit in the DDRD register selects the direction of this pin. If DDDn is set (one), PDn is con-
figured as an output pin. If DDDn is cleared (zero), PDn is configured as an input pin. If PDn is set (one) when configured
as an input pin the MOS pull up resistor is activated. To switch the pull up resistor off the PDn has to be cleared (zero) or
the pin has to be configured as an output pin. The port pins are tri-stated when a reset condition becomes active, even if
the clock is not running.
Bit 76543210
$12 PORTD7 PORTD6 PORTD5 PORTD4 PORTD3 PORTD2 PORTD1 PORTD0 PORTD
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$11 DDD7 DDD6 DDD5 DDD4 DDD3 DDD2 DDD1 DDD0 DDRD
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$10 PIND7 PIND6 PIND5 PIND4 PIND3 PIND2 PIND1 PIND0 PIND
Read/WriteRRRRRRRR
Initial Value High-Z High-Z High-Z High-Z High-Z High-Z High-Z High-Z
AT94K Family
127
.
Note: 1. n: 7,6...0, pin number
Figure 62. PortD Schematic Diagram
Table 39. DDDn(1) Bits on PortD Pins
DDDn(1) PORTDn(1) I/O Pull-up Comment
0 0 Input No Tri-state (High-Z)
0 1 Input Yes PDn will Source Current if External Pulled Low
1 0 Output No Push-pull Zero Output
1 1 Output No Push-pull One Output
PD*
DATA BUS
RL
WL
DDD*
Q D
R
PORTD*
Q D
R
RESET
RESET
WD
RD
RP
GTS
DL
MOS
PULLUP
RESET
DL
GTS: Global Tri-State
DL: Configuration Download
WL: Write PORTD
WD: Write DDRD
RL: Read PORTD Latch
RD: Read DDRD
RP: Read PORTD Pin
AT94K Family
128
PortE
PortE is an 8-bit bi-directional I/O port with internal pull-up resistors.
Three I/O memory address locations are allocated for the PortE, one each for the Data Register PORTE, $07($27), Data
Direction Register DDRE, $06($26) and the PortE Input Pins PINE, $05($25). The PortE Input Pins address is read
only, while the Data Register and the Data Direction Register are read/write.
The PortE output buffers can sink 20 mA. As inputs, PortE pins that are externally pulled low will source current if the pull-
up resistors are activated.
All PortE pins have alternate functions as shown in the following table:
When the pins are used for the alternate function the DDRE and PORTE register has to be set according to the alternate
function description.
PortE Data Register PORTE
PortE Data Direction Register DDRE
PortE Input Pins Address PINE
The PortE Input Pins address PINE is not a register, and this address enables access to the physical value on each
PortE pin. When reading PORTE, the PortE Data Latch is read, and when reading PINE, the logical values present on the
pins are read.
Table 40. PortE Pins Alternate Functions Controlled by SCR and AVR I/O Registers
Port Pin Alternate Function Input Output
PE0 TX0 (UART0 Transmit Pin) External Timer0 Clock -
PE1 RX0 (UART0 Receive Pin) - Output Compare Timer0/PWM0
PE2 TX1 (UART1 Transmit Pin) - -
PE3 RX1 (UART1 Receive Pin) - Output Compare Timer2/PWM2
PE4 INT0 (External Interrupt0 Input) External Timer1 Clock -
PE5 INT1 (External Interrupt0 Input) - Output Compare Timer1B/PWM1B
PE6 INT2 (External Interrupt0 Input) - Output Compare Timer1A/PWM1A
PE7 INT3 (External Interrupt0 Input) Input Capture Counter1
Bit 76543210
$07 ($27) PORTE7 PORTE6 PORTE5 PORTE4 PORTE3 PORTE2 PORTE1 PORTE0 PORTE
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$06 ($26) DDE7 DDE6 DDE5 DDE4 DDE3 DDE2 DDE1 DDE0 DDRE
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
$05 ($25) PINE7 PINE6 PINE5 PINE4 PINE3 PINE2 PINE1 PINE0 PINE
Read/WriteRRRRRRRR
Initial Value High-Z High-Z High-Z High-Z High-Z High-Z High-Z High-Z
AT94K Family
129
PortE as General Digital I/O
PEn, General I/O pin: The DDEn bit in the DDRE register selects the direction of this pin. If DDEn is set (one), PEn is con-
figured as an output pin. If DDEn is cleared (zero), PEn is configured as an input pin. If PEn is set (one) when configured as
an input pin, the MOS pull up resistor is activated. To switch the pull up resistor off the PEn has to be cleared (zero) or the
pin has to be configured as an output pin. The port pins are tri-stated when a reset condition becomes active, even if the
clock is not running.
Note: 1. n: 7,6...0, pin number
Alternate Functions of PortE
PortE, Bit 0
UART0 Transmit Pin.
PortE, Bit 1
UART0 Receive Pin. Receive Data (Data input pin for the UART0). When the UART0 receiver is enabled this pin is config-
ured as an input regardless of the value of DDRE0. When the UART0 forces this pin to be an input, a logic 1 in PORTE0
will turn on the internal pull-up.
PortE, Bit 2
UART1 Transmit Pin.
The alternate functions of Port E as UART0 pins are enabled by setting bit SCR52 in the FPSLIC System Control Register.
This is necessary only in smaller pinout packages where the UART signals are not bonded out. The alternate functions of
Port E as UART1 pins are enabled by setting bit SCR53 in the FPSLIC System Control Register.
PortE, Bit 3
UART1 Receive Pin. Receive Data (Data input pin for the UART1). When the UART1 receiver is enabled this pin is config-
ured as an input regardless of the value of DDRE2. When the UART1 forces this pin to be an input, a logic 1 in PORTE2
will turn on the internal pull-up.
PortE, Bit 4-7
External Interrupt sources 0/1/2/3: The PE4 - PE7 pins can serve as external interrupt sources to the MCU. Interrupts can
be triggered by low-level on these pins. The internal pull-up MOS resistors can be activated as described above.
The alternate functions of PortE as Interrupt pins by setting a bit in the System Control Register. INT0 is controlled by
SCR48. INT1 is controlled by SCR49. INT2 is controlled by SCR50. INT3 is controlled by SCR51.
PortE, Bit 7 also shares a pin with the configuration control signal CHECK. Lowering CON to initiate an FPSLIC download
(whether for loading or Checking) causes the PE7/CHECK pin to immediately tri-state. This function happens only if the
Check pin has been enabled in the system control register. The use of the Check pin will NOT disable the use of that pin as
an input to PE7 nor as an input as alternate INT3.
Alternate I/O Functions of PortE
PortE may also be used for various Timer/Counter functions, such as External Input Clocks (TC0 and TC1), Input Capture
(TC1), Pulse Width Modulation (TC0, TC1 and TC2), and toggling upon an Output Compare (TC0, TC1 and TC2). For a
detailed pinout description, consult Table 40 on page 128. For more information on the function of each pin, please consult
the Timer/Counter section of the datasheet, beginning on page 65.
Table 41. DDEn(1) Bits on PortE Pins
DDEn(1) PORTEn(1) I/O Pull-up Comment
0 0 Input No Tri-state (High-Z)
0 1 Input Yes PDn(1) will source current if external pulled low.
1 0 Output No Push-pull Zero Output
1 1 Output No Push-pull One Output
AT94K Family
130
PortE Schematics
Note that all port pins are synchronized. The synchronization latches are, however, not shown in the figures.
Figure 63. PortE Schematic Diagram (Pin PE0)
PE0
TX0D
DATA BUS
GTS
DL
SCR(52)
MOS
PULL-UP
RL
WL
DDE0
Q D
R
PORTE0
Q D
R
RESET
RESET
WD
RD
RP
GTS: Global Tri-S tate
DL: Configuration Download
WL: Write PORTE
WD: Write DDRE
RL: Read PORTE Latch
RD: Read DDRE
RP: Read PORTE Pin
TX0D: UART 0 Transmit Data
TX0ENABLE: UART 0 Transmit Enable
SCR: System Control Register
T0: Timer/Counter0 Clock
1
0
T0
TX0
MOS
PULL-UP
TX0D
SCR(52)
TX0ENABLE
TX0ENABLE
RESET
DL
DL
RESET
DL
GTS
AT94K Family
131
Figure 64. PortE Schematic Diagram (Pin PE1)
PE1
DATA BUS
GTS
DL
SCR(52)
RL
WL
DDE1
Q D
R
PORTE1
Q D
R
RESET
RESET
WD
RD
RP
GTS: Global Tri-State
DL: Configuration Download
WL: Write PORTE
WD: Write DDRE
RL: Read PORTE Latch
RD: Read DDRE
RP: Read PORTE Pin
RX0D: UART 0 Receive Data
SCR: System Control Register
OC0/PMW0: Timer/Counter 0 Output Compare
COM0*: Timer/Counter0 Control Bits
RX0
RX0D
SCR(52)
0
1
MOS
PULL-UP
OC0/PMW0
1
0
COM00
COM01
MOS
PULL-UP
RESET
DL
AT94K Family
132
Figure 65. PortE Schematic Diagram (Pin PE2)
PE2
DATA BUS
RL
WL
DDE2
Q D
R
PORTE2
Q D
R
RESET
RESET
WD
RD
RP
GTS: Global Tri-State
DL: Configuration Download
WL: Write PORTE
WD: Write DDRE
RL: Read PORTE Latch
RD: Read DDRE
RP: Read PORTE Pin
TX1D: UART 1 Transmit Data
TX1ENABLE: UART 1 Transmit Enable
SCR: System Control Register
TX1D
GTS
DL
SCR(53)
1
0
TX1ENABLE
MOS
PULL-UP
RESET
DL
TX1
MOS
PULL-UP
TX1D
SCR(53)
TX1ENABLE
DL
RESET
DL
GTS
AT94K Family
133
Figure 66. PortE Schematic Diagram (Pin PE3)
PE3
DATA BUS
GTS
DL
SCR(53)
RL
WL
DDE3
Q D
R
PORTE3
Q D
R
RESET
RESET
WD
RD
RP
GTS: Global Tri-State
DL: Configuration Download
WL: Write PORTE
WD: Write DDRE
RL: Read PORTE Latch
RD: Read DDRE
RP: Read PORTE Pin
RX1D: UART 1 Receive Data
SCR: System Control Register
OC2/PMW2: Timer/Counter 2 Output Compare
COM2*: Timer/Counter2 Control Bits
RX1
RX1D
SCR(53)
0
1
MOS
PULL-UP
OC2/PMW2
1
0
COM20
COM21
MOS
PULL-UP
RESET
DL
AT94K Family
134
Figure 67. PortE Schematic Diagram (Pin PE4)
PE4
DATA BUS
GTS
DL
SCR(48)
RL
DDE4
Q D
R
RESET
WD
RD
RP
GTS: Global Tri-State
DL: Configuration Download
WL: Write PORTE
WD: Write DDRE
RL: Read PORTE Latch
RD: Read DDRE
RP: Read PORTE Pin
extintp0: External Interrupt 0
SCR: System Control Register
T1: Timer/Counter1 External Clock
INTP0
extintp0
SCR(48)
0
1
MOS
PULL-UP
WL
PORTE4
Q D
R
RESET
T1
MOS
PULL-UP
RESET
DL
AT94K Family
135
Figure 68. PortE Schematic Diagram (Pin PE5)
PE5
DATA BUS
GTS
DL
SCR(49)
RL
DDE5
Q D
R
RESET
WD
RD
RP
GTS: Global Tri-State
DL: Configuration Download
WL: Write PORTE
WD: Write DDRE
RL: Read PORTE Latch
RD: Read DDRE
RP: Read PORTE Pin
extintp1: External Interrupt 1
SCR: System Control Register
OC1B: Timer/Counter1 Output Compare B
COM1B*: Timer/Counter1 B Control Bits
INTP1
extintp1
SCR(49)
0
1
MOS
PULL-UP
WL
PORTE5
Q D
R
RESET
OC1B
COM1B0
COM1B1
1
0
MOS
PULL-UP
RESET
DL
AT94K Family
136
Figure 69. PortE Schematic Diagram (Pin PE6)
PE6
DATA BUS
GTS
DL
SCR(50)
RL
DDE6
Q D
R
RESET
WD
RD
RP
GTS: Global Tri-State
DL: Configuration Download
WL: Write PORTE
WD: Write DDRE
RL: Read PORTE Latch
RD: Read DDRE
RP: Read PORTE Pin
extintp2: External Interrupt 2
SCR: System Control Register
OC1A: Timer/Counter1 Output Compare A
COM1A*: Timer/Counter1 A Control Bits
INTP2
extintp2
SCR(50)
0
1
MOS
PULL-UP
WL
PORTE6
Q D
R
RESET
OC1A
COM1A0
COM1A1
1
0
MOS
PULL-UP
RESET
DL
AT94K Family
137
Figure 70. PortE Schematic Diagram (Pin PE7)
PE7
DATA BUS
GTS
DL
SCR(51)
RL
DDE7
Q D
R
RESET
WD
RD
RP
GTS: Global Tri-State
DL: Configuration Download
WL: Write PORTE
WD: Write DDRE
RL: Read PORTE Latch
RD: Read DDRE
RP: Read PORTE Pin
extintp3: External Interrupt 3
SCR: System Control Register
ICP: Timer/Counter Input Capture Pin
INTP3
extintp3
SCR(51)
0
1
MOS
PULL-UP
WL
PORTE7
Q D
R
RESET
ICP
MOS
PULL-UP
RESET
DL
AT94K Family
138
Section 4 AC & DC TIMING CHARACTERISTICS
Note: 1. Minimum voltage of -0.5V DC which may undershoot to -2.0V for pulses of less than 20 ns.
*NOTICE: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a
stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the oper-
ational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods
may affect device reliability.
Absolute Maximum Ratings 3.3V Commercial/Industrial*
Symbol Parameter Conditions Min Max Units
VCC Supply Voltage With respect to GND -0.5 4.0V V
VIDC Input Voltage(1) With respect to GND -0.5 4.0V V
VODC Output Voltage With respect to GND -0.5 4.0V V
TSTG Storage Temperature -65°C+150°C
TJJunction Temperature +150°C
TLLead Temperature (Soldering, 10 sec.) +250°C
ESD RZAP = 1.5K, CZAP = 100 pF 2000 V
DC and AC Operating Range 3.3V Operation
AT94K
Commercial
AT94K
Industrial
Operating Temperature (Case) 0°C - 70°C-40°C - 85°C
VCC Power Supply 3.3V ± 0.3V 3.3V ± 0.3V
Input Voltage Level (CMOS) High (VIHC) 70% - 100% VCC 70% - 100% VCC
Low (VILC) 0 - 30% VCC 0 - 30% VCC
AT94K Family
139
Notes: 1. Complete FPSLIC device with static FPGA core (no clock in FPGA active).
2. Max means the highest value where the pin is guaranteed to be read as low.
3. Min means the lowest value where the pin is guaranteed to be read as high.
DC Characteristics 3.3V Operation Commercial/Industrial (Preliminary)
TA = -40°C to 85°C, VCC = 2.7V to 3.6V (unless otherwise noted(1))
Symbol Parameter Conditions Min Typ Max Units
VIH High-level Input Voltage
CMOS 70% VCC V
TTL 2.0 V
VIH1 Input High-voltage XTAL 0.7 VCC(3) VCC + 0.5 V
VIH2 Input High-voltage RESET 0.85 VCC(3) VCC + 0.5 V
VIL Low-level Input Voltage
CMOS -0.3 30% VCC V
TTL -0.3 0.8 V
VIL1 Input Low-voltage XTAL -0.5 0.1(2) V
VOH High-level Output Voltage
IOH = 4 mA
VCC = VCC min 2.1 –– V
IOH = 12 mA
VCC = 3.0V 2.1 –– V
IOH = 16 mA
VCC = 3.0V 2.1 –– V
VOL Low-level Output Voltage
IOL = -4 mA
VCC = 3.0V ––0.4 V
IOL = -12 mA
VCC = 3.0V ––0.4 V
IOL = -16 mA
VCC = 3.0V ––0.4 V
RRST Reset Pull-up 100 500 k
RI/O I/O Pin Pull-up 35 120 k
IIH High-level Input Current
VIN = VCC max ––10 µA
With pull-down, VIN = VCC 75 150 300 µA
IIL Low-level Input Current
VIN = VSS -10 ––µA
With pull-up, VIN = VSS -300 -150 -75 µA
IOZH
High-level Tri-state Output leakage
current
Without pull-down, VIN = VCC max 10 µA
With pull-down, VIN = VCC max 75 150 300 µA
IOZL Low-level Tri-state Output leakage current
Without pull-up, VIN = VSS -10 µA
With pull-up, VIN = VSS -300 -150 -75 µA
ICC
Standby Current Consumption Standby, unprogrammed 0.6 0.5 mA
Power Supply Current
Idle, VCC = 3V(1) 1.0 mA
Power-down, VCC = 3V(1)
WDT Enable 80 800 µA
Power-down, VCC = 3V(1)
WDT Disable 50 500 µA
Power-save, VCC = 3V(1)
WDT Disable 80 800 µA
FPGA Core Current Consumption 2mA/MHz
CIN Input Capacitance All Pins ––10 pF
AT94K Family
140
FPSLIC Dual-port SRAM Characteristics
The Dual-port SRAM operates in single-edge clock controlled mode during read operations, and a double-edge controlled
mode during write operations. Addresses are clocked internally on the rising edge of the clock signal (ME). Any change of
address without a rising edge of ME is not considered.
In read mode, the rising clock edge triggers data read without any significant constraint on the length of the clock pulse.
The WE signal must be changed and held low before the rising edge of ME to signify a read cycle. The WE signal should
then remain low until the falling edge of the clock.
In write mode, data applied to the inputs is latched on either the falling edge of WE or the falling edge of the clock, which-
ever comes earlier, and written to memory. Also, WE must be high before the rising edge of ME to signify a write cycle. If
data inputs change during a write cycle, only the value present at the write end is considered and written to the address
clocked at the ME rise. A write cycle ending on WE fall does not turn into a read cycle the next cycle will be a read cycle
if WE remains low during rising edge of ME.
Figure 71. SRAM Read Cycle Timing Diagram
Figure 72. SRAM Write Cycle Timing Diagram
Frame Interface
The FPGA Frame Clock phase is selectable (see System Control Register FPGA/AVRon page 30). This document
refers to the clock at the AVR SRAM interface as ME (the relation of ME to data, address and write enable does not
change). By default, FrameClock is inverted (ME = ~FrameClock)> Selecting the non-inverted phase assigns ME = Frame-
Clock. The AVR SRAM operates in single-edge clock controlled mode during read operations, and double-edge clock
controlled mode during writes. Addresses are clocked internally on the rising edge of the clock signal (ME). Any change of
address without a rising edge of ME is not considered.
Address Valid
tt
t
t
t
t
t
Previous Data Output Valid
ADDR
CLK (ME)
WE
DATA READ
- Address Setup
- Address Hold
- Read Cycle Setup
- Read Cycle Hold
- Access Time from posedge ME
- Minimum ME High
- Minimum ME Low
ADS ADH
MEL
RDS
MEH
RDH
ACC
t
t
t
t
t
t
t
ADS
ADH
RDS
RDH
ACC
MEH
MEL
Address Valid
tt
t
ADDR
CLK (ME)
t
t
t
t
t
t
Data Valid
WE
DATA WRITE
- Address Setup
- Address Hold
- Write Cycle Setup
- Minimum Write Duration
- Data Setup to Write End
- Data Hold to Write End
ADS ADH
MPW
MPW
WRS
WDS
WDS
WDH
WDH
t
t
t
t
t
t
ADS
ADH
WRS
MPW
WDS
WDH
AT94K Family
141
Table 42. SRAM Read Cycle Timing Numbers
Commercial 3.3V ± 10%/Industrial 3.3V ± 10%
Symbol Parameter
Commercial Industrial
UnitsMin Typ Max Min Typ Max
tADS Address Setup 0.6 0.8 1.1 0.5 0.8 1.2 ns
tADH Address Hold 0.7 0.9 1.3 0.6 0.9 1.5 ns
tRDS Read Cycle Setup 000000ns
tRDH Read Cycle Hold 000000ns
tACC Access Time from Posedge ME 3.4 4.2 5.9 2.9 4.2 6.9 ns
tMEH Minimum ME High 0.7 0.9 1.3 0.6 0.9 1.5 ns
tMEl Minimum ME Low 0.6 0.8 1.1 0.6 0.8 1.3 ns
Table 43. SRAM Write Cycle Timing Numbers
Commercial 3.3V ± 10%/Industrial 3.3V ± 10%
Symbol Parameter
Commercial Industrial
UnitsMin Typ Max Min Typ Max
tADS Address Setup 0.6 0.8 1.1 0.5 0.8 1.2 ns
tADH Address Hold 0.7 0.9 1.3 0.6 0.9 1.5 ns
tWRS Write Cycle Setup 000000ns
tMPW Minimum Write Duration 1.4 1.8 2.5 1.2 1.8 3.0 ns
tWDS Data Setup to Write End 4.6 5.7 8.0 3.9 5.7 9.4 ns
tWDH Data Hold to Write End 0.6 0.8 1.1 0.5 0.8 1.3 ns
AT94K Family
142
Note: 1. Insertion delays are specified from XTAL2. These delays are more meaningful because the XTAL1-to-XTAL2 delay is sensi-
tive to system loading on XTAL2. If it is necessary to drive external devices with the system clock, devices should use
XTAL2 output pin. Remember that XTAL2 is inverted in comparison to XTAL1.
Table 44. FPSLIC Interface Timing Information(1)
Parameter Description
3.3V Commercial ± 10% 3.3V Industrial ± 10%
UnitsMin Typ Max Min Typ Max
tIXG4 Clock Delay From XTAL2 Pad to
GCK_5 Access to FPGA Core
3.6 4.8 7.6 3.4 4.8 7.9 ns
tIXG5 Clock Delay From XTAL2 Pad to
GCK_6 Access to FPGA Core
3.9 5.2 8.1 3.6 5.2 8.8 ns
tIXC Clock Delay From XTAL2 Pad to
AVR Core Clock
2.8 3.7 6.3 2.5 3.7 6.9 ns
tIXI Clock Delay From XTAL2 Pad to
AVR I/O Clock
3.5 4.7 7.5 3.2 4.7 7.8 ns
tCFIR AVR Core Clock to FPGA I/O
Read Enable
5.3 6.6 7.9 4.4 6.6 9.2 ns
tCFIW AVR Core Clock to FPGA I/O Write
Enable
5.2 6.6 7.9 4.4 6.6 9.2 ns
tCFIS AVR Core Clock to FPGA I/O
Select Active
6.3 7.8 9.4 5.3 7.8 11.0 ns
tFIRQ FPGA Interrupt Net Propagation
Delay to AVR Core
0.2 0.2 0.3 0.1 0.2 0.3 ns
tIFS FPGA SRAM Clock to On-chip
SRAM
6.1 7.7 7.7 4.9 7.7 7.7 ns
tFRWS FPGA SRAM Write Stobe to
On-chip SRAM
4.4 5.5 5.5 3.7 5.5 5.5 ns
tFAS FPGA SRAM Address Valid to
On-chip SRAM Address Valid
5.4 6.7 6.7 4.3 6.7 6.7 ns
tFDWS FPGA Write Data Valid to On-chip
SRAM Data Valid
1.3 1.7 2.0 1.3 1.7 2.0 ns
tFDRS On-chip SRAM Data Valid to
FPGA Read Data Valid
0.2 0.2 0.2 0.2 0.2 0.2 ns
AT94K Family
143
External Clock Drive Waveforms
Figure 73. External Clock Drive Waveforms
VIL1
VIH1
Table 45. External Clock Drive, VCC = 3.0V to 3.6V
Symbol Parameter Min Max Units
1/tCLCL Oscillator Frequency 0 25 MHz
tCLCL Clock Period 40 ns
tCHCX High Time 15 ns
tCLCX Low Time 15 ns
tCLCH Rise Time 1.6 µs
tCHCL Fall Time 1.6 µs
AT94K Family
144
AC Timing Characteristics 3.3V Operation
Delays are based on fixed loads and are described in the notes.
Maximum times based on worst case: VCC = 3.00V, temperature = 70°C
Minimum times based on best case: VCC = 3.60V, temperature = 0°C
Max delays are the average of tPDLH and tPDHL.
Cell Function Parameter Path -25 Units Notes
Core
2 Input Gate tPD (max) x/y -> x/y 2.9 ns 1 Unit Load
3 Input Gate tPD (max) x/y/z -> x/y 2.8 ns 1 Unit Load
3 Input Gate tPD (max) x/y/w -> x/y 3.4 ns 1 Unit Load
4 Input Gate tPD (max) x/y/w/z -> x/y 3.4 ns 1 Unit Load
Fast Carry tPD (max) y -> y 2.3 ns 1 Unit Load
Fast Carry tPD (max) x -> y 2.9 ns 1 Unit Load
Fast Carry tPD (max) y -> x 3.0 ns 1 Unit Load
Fast Carry tPD (max) x -> x 2.3 ns 1 Unit Load
Fast Carry tPD (max) w -> y 3.4 ns 1 Unit Load
Fast Carry tPD (max) w -> x 3.4 ns 1 Unit Load
Fast Carry tPD (max) z -> y 3.4 ns 1 Unit Load
Fast Carry tPD (max) z -> x 2.4 ns 1 Unit Load
DFF tPD (max) q -> x/y 2.8 ns 1 Unit Load
DFF tsetup (min) x/y -> clk ––
DFF thold (min) x/y -> clk ––
DFF tPD (max) R -> x/y 3.2 ns 1 Unit Load
DFF tPD (max) S -> x/y 3.0 ns 1 Unit Load
DFF tPD (max) q -> w 2.7 ns
incremental -> L tPD (max) x/y -> L 2.4 ns
Local Output Enable tPZX (max) oe -> L 2.8 ns 1 Unit Load
Local Output Enable tPXZ (max) oe -> L 2.4 ns
AT94K Family
145
AC Timing Characteristics 3.3V Operation
Delays are based on fixed loads and are described in the notes.
Maximum times based on worst case: VCC = 3.0V, temperature = 70°C
Minimum times based on best case: VCC = 3.6V, temperature = 0°C
Max delays are the average of tPDLH and tPDHL.
All input IO characteristics measured from a VIH of 50% of VDD at the pad (CMOS threshold) to the internal VIH of 50% of
VDD. All output IO characteristics are measured as the average of tPDLH and tPDHL to the pad VIH of 50% of VDD.
Cell Function Parameter Path -25 Units Notes
Repeaters
Repeater tPD (max) L -> E 2.2 ns 1 Unit Load
Repeater tPD (max) E -> E 2.2 ns 1 Unit Load
Repeater tPD (max) L -> L 2.2 ns 1 Unit Load
Repeater tPD (max) E -> L 2.2 ns 1 Unit Load
Repeater tPD (max) E -> IO 1.4 ns 1 Unit Load
Repeater tPD (max) L -> IO 1.4 ns 1 Unit Load
All input IO characteristics measured from a VIH of 50% of VDD at the pad (CMOS threshold) to the internal VIH of 50% of
VDD. All output IO characteristics are measured as the average of tPDLH and tPDHL to the pad VIH of 50% of VDD.
Cell Function Parameter Path -25 Units Notes
IO
Input tPD (max) pad -> x/y 1.9 ns No Extra Delay
Input tPD (max) pad -> x/y 5.8 ns 1 Extra Delay
Input tPD (max) pad -> x/y 11.5 ns 2 Extra Delays
Input tPD (max) pad -> x/y 17.4 ns 3 Extra Delays
Output, Slow tPD (max) x/y/E/L -> pad 9.1 ns 50 pf Load
Output, Medium tPD (max) x/y/E/L -> pad 7.6 ns 50 pf Load
Output, Fast tPD (max) x/y/E/L -> pad 6.2 ns 50 pf Load
Output, Slow tPZX (max) oe -> pad 9.5 ns 50 pf Load
Output, Slow tPXZ (max) oe -> pad 2.1 ns 50 pf Load
Output, Medium tPZX (max) oe -> pad 7.4 ns 50 pf Load
Output, Medium tPXZ (max) oe -> pad 2.7 ns 50 pf Load
Output, Fast tPZX (max) oe -> pad 5.9 ns 50 pf Load
Output, Fast tPXZ (max) oe -> pad 2.4 ns 50 pf Load
AT94K Family
146
AC Timing Characteristics 3.3V Operation
Delays are based on fixed loads and are described in the notes.
Maximum times based on worst case: VCC = 3.0V, temperature = 70°C
Minimum times based on best case: VCC = 3.6V, temperature = 0°C
Max delays are the average of tPDLH and tPDHL.
Clocks and Reset Input buffers are measured from a VIH of 1.5V at the input pad to the internal VIH of 50% of VCC.
Maximum times for clock input buffers and internal drivers are measured for rising edge delays only.
Cell Function Parameter Path Device -25 Units Notes
Global Clocks and Set/Reset
GCK Input Buffer tPD (max) pad -> clock
pad -> clock
AT94K05
AT94K10
AT94K40
1.2
1.5
1.9
ns
ns
Rising Edge Clock
FCK Input Buffer tPD (max) pad -> clock
pad -> clock
AT94K05
AT94K10
AT94K40
0.7
0.8
0.9
ns
ns
Rising Edge Clock
Clock Column Driver tPD (max) clock -> colclk
clock -> colclk
AT94K05
AT94K10
AT94K40
1.3
1.8
2.5
ns
ns
Rising Edge Clock
Clock Sector Driver tPD (max) colclk -> secclk
colclk -> secclk
AT94K05
AT94K10
AT94K40
1.0
1.0
1.0
ns
ns
Rising Edge Clock
GSRN Input Buffer tPD (max) colclk -> secclk
colclk -> secclk
AT94K05
AT94K10
AT94K40
5.4
8.2
ns
ns
Global Clock to Output tPD (max) clock pad -> out
clock pad -> out
AT94K05
AT94K10
AT94K40
12.6
13.4
14.5
ns
ns
Rising Edge Clock
Fully Loaded Clock Tree
Rising Edge DFF
20 mA Output Buffer
50 pf Pin Load
Fast Clock to Output tPD (max) clock pad -> out
clock pad -> out
AT94K05
AT94K10
AT94K40
12.1
12.7
13.5
ns
ns
Rising Edge Clock
Fully Loaded Clock Tree
Rising Edge DFF
20 mA Output Buffer
50 pf Pin Load
AT94K Family
147
CMOS buffer delays are measured from a VIH of 1/2 VCC at the pad to the internal VIH at A. The input buffer load is con-
stant. Buffer delay is to a pad voltage of 1.5V with one output switching. Parameter based on characterization and
simulation; not tested in production. An FPGA power calculation is available in Atmels System Designer software (see also
page 139).
AC Timing Characteristics 3.3V Operation
Delays are based on fixed loads and are described in the notes.
Maximum times based on worst case: VCC = 3.0V, temperature = 70°C
Minimum times based on best case: VCC = 3.6V, temperature = 0°C
Cell Function Parameter Path -25 Units Notes
Async RAM
Write tWECYC (min) cycle time 12.0 ns
Write tWEL (min) we 5.0 ns Pulse Width Low
Write tWEH (min) we 5.0 ns Pulse Width High
Write tsetup (min) wr addr setup-> we 5.3 ns
Write thold (min) wr addr hold -> we 0.0 ns
Write tsetup (min) din setup -> we 5.0 ns
Write thold (min) din hold -> we 0.0 ns
Write thold (min) oe hold -> we 0.0 ns
Write/Read tPD (max) din -> dout 8.7 ns rd addr = wr addr
Read tPD (max) rd addr -> dout 6.3 ns
Read tPZX (max) oe -> dout 2.9 ns
Read tPXZ (max) oe -> dout 3.5 ns
Sync RAM
Write tCYC (min) cycle time 12.0 ns
Write tCLKL (min) clk 5.0 ns
Write tCLKH (min) clk 5.0 ns Pulse Width High
Write tsetup (min) we setup-> clk 3.2 ns
Write thold (min) we hold -> clk 0.0 ns
Write tsetup (min) wr addr setup-> clk 5.0 ns
Write thold (min) wr addr hold -> clk 0.0 ns
Write tsetup (min) wr data setup-> clk 3.9 ns
Write thold (min) wr data hold -> clk 0.0 ns
Write/Read tPD (max) din -> dout 8.7 ns rd addr = wr addr
Write/Read tPD (max) clk -> dout 5.8 ns rd addr = wr addr
Read tPD (max) rd addr -> dout 6.3 ns
Read tPZX (max) oe -> dout 2.9 ns
Read tPXZ (max) oe -> dout 3.5 ns
AT94K Family
148
Section 5 Packaging and Pin List Information
Table 46. Part and Package Combinations Available
Part # Package AT94K05 AT94K10 AT94K40
PLCC 84 AJ 46 46 46
TQ 100 AQ585856
LQ144 BQ828484
PQ 208 DQ 96 116 120
Table 47. AT94K Pin List
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
West Side
GND GND GND 12 1 1 2
I/O1, GCK1 (A16) I/O1, GCK1 (A16) I/O1, GCK1 (A16) 13 2 2 4
I/O2 (A17) I/O2 (A17) I/O2 (A17) 14 3 3 5
I/O3 I/O3 I/O3 4 6
I/O4 I/O4 I/O4 5 7
I/O5 (A18) I/O5 (A18) I/O5 (A18) 15 4 6 8
I/O6 (A19) I/O6 (A19) I/O6 (A19) 16 5 7 9
GND
I/O7
I/O8
I/O9
I/O10
I/O11
I/O12
VCC(1)
GND
I/O13
I/O14
I/O7 I/O7 I/O15 10
I/O8 I/O8 I/O16 11
I/O9 I/O17 12
I/O10 I/O18 13
GND
I/O19
I/O20
I/O11 I/O21
AT94K Family
149
I/O12 I/O22
I/O23
I/O24
GND GND GND 8 14
I/O9, FCK1 I/O13, FCK1 I/O25, FCK1 9 15
I/O10 I/O14 I/O26 10 16
I/O11 (A20) I/O15 (A20) I/O27 (A20) 17 6 11 17
I/O12 (A21) I/O16 (A21) I/O28 (A21) 18 7 12 18
VCC(1) VCC(1)
I/O17 I/O29
I/O18 I/O30
GND
I/O31
I/O32
I/O33
I/O34
I/O35
I/O36
GND
VCC(1)
I/O37
I/O38
I/O39
I/O40
I/O19 I/O41 19
I/O20 I/O42 20
GND
I/O13 I/O21 I/O43 13 21
I/O14 I/O22 I/O44 8 14 22
I/O45
I/O46
I/O15 (A22) I/O23 (A22) I/O47 (A22) 19 9 15 23
I/O16 (A23) I/O24 (A23) I/O48 (A23) 20 10 16 24
GND GND GND 21 11 17 25
VDD(2) VDD(2) VDD(2) 22 12 18 26
I/O17 (A24) I/O25 (A24) I/O49 (A24) 23 13 19 27
I/O18 (A25) I/O26 (A25) I/O50 (A25) 24 14 20 28
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
150
I/O51
I/O52
I/O19 I/O27 I/O53 15 21 29
I/O20 I/O28 I/O54 22 30
GND
I/O29 I/O55 31
I/O30 I/O56 32
I/O57
I/O58
I/O59
I/O60
VCC(1)
GND
I/O61
I/O62
I/O63
I/O64
I/O65
I/O66
GND
I/O31 I/O67
I/O32 I/O68
VDD(2) VDD(2)
I/O21 (A26) I/O33 (A26) I/O69 (A26) 25 16 23 33
I/O22 (A27) I/O34 (A27) I/O70 (A27) 26 17 24 34
I/O23 I/O35 I/O71 25 35
I/O24, FCK2 I/O36, FCK2 I/O72, FCK2 26 36
GND GND GND 27 37
I/O73
I/O74
I/O37 I/O75
I/O38 I/O76
I/O77
I/O78
GND
I/O79
I/O80
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
151
I/O39 I/O81 38
I/O40 I/O82 39
I/O25 I/O41 I/O83 40
I/O26 I/O42 I/O84 41
GND
VCC(1)
I/O85
I/O86
I/O87
I/O88
I/O27 (A28) I/O43 (A28) I/O89 (A28) 27 18 28 42
I/O28 I/O44 I/O90 19 29 43
GND
I/O91
I/O92
I/O29 I/O45 I/O93 30 44
I/O30 I/O46 I/O94 31 45
I/O31 (OTS) I/O47 (OTS) I/O95 (OTS) 28203246
I/O32, GCK2 (A29) I/O48, GCK2 (A29) I/O96, GCK2 (A29) 29 21 33 47
AVRRESET AVRRESET AVRRESET 30 22 34 48
GND GND GND 31 23 35 49
M0 M0 M0 32 24 36 50
South Side
VCC(1) VCC(1) VCC(1) 33 25 37 55
M2 M2 M2 34 26 38 56
I/O33, GCK3 I/O49, GCK3 I/O97, GCK3 35 27 39 57
I/O34 (HDC) I/O50 (HDC) I/O98 (HDC) 36 28 40 58
I/O35 I/O51 I/O99 41 59
I/O36 I/O52 I/O100 42 60
I/O37 not a user I/O I/O53 not a user I/O I/O101 29 43 61
I/O38 (LDC) I/O54 (LDC) I/O102 (LDC) 37 30 44 62
GND
I/O103
I/O104
I/O105
I/O106
I/O107
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
152
I/O108
VCC(1)
GND
I/O39 I/O55 I/O109 63
I/O40 I/O56 I/O110 64
I/O57 I/O111 65
I/O58 I/O112 66
I/O113
I/O114
GND
I/O115
I/O116
I/O59 I/O117
I/O60 I/O118
I/O119
I/O120
GND GND GND 45 67
I/O41 I/O61 I/O121 46 68
I/O42 I/O62 I/O122 47 69
I/O43 I/O63 I/O123 38 31 48 70
I/O44 I/O64 I/O124 39 32 49 71
VCC(1) VCC(1)
I/O65 I/O125 72
I/O66 I/O126 73
GND
I/O127
I/O128
I/O129
I/O130
I/O131
I/O132
GND
VCC(1)
I/O133
I/O134
I/O67 I/O135
I/O68 I/O136
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
153
I/O45 I/O69 I/O137 33 50 74
I/O46 I/O70 I/O138 34 51 75
GND
I/O139
I/O140
I/O141
I/O142
I/O47 (TD7) I/O71 (TD7) I/O143 (TD7) 40 35 52 76
I/O48 (InitErr) I/O72 (InitErr) I/O144 (InitErr) 41 36 53 77
VDD(2) VDD(2) VDD(2) 42 37 54 78
GND GND GND 43 38 55 79
I/O49 (TD6) I/O73 (TD6) I/O145 (TD6) 44 39 56 80
I/O50 (TD5) I/O74 (TD5) I/O146 (TD5) 45 40 57 81
I/O147
I/O148
I/O149
I/O150
GND
I/O51 I/O75 I/O151 41 58 82
I/O52 I/O76 I/O152 42 59 83
I/O77 I/O153 84
I/O78 I/O154 85
I/O155
I/O156
VCC(1)
GND
I/O157
I/O158
I/O159
I/O160
I/O161
I/O162
GND
I/O79 I/O163
I/O80 I/O164
VCC(1) VCC(1)
I/O53 (TD4) I/O81 (TD4) I/O165 (TD4) 46 43 60 86
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
154
I/O54 (TD3) I/O82 (TD3) I/O166 (TD3) 47 44 61 87
I/O55 I/O83 I/O167 62 88
I/O56 I/O84 I/O168 63 89
GND GND GND 64 90
I/O169
I/O170
I/O85 I/O171
I/O86 I/O172
I/O173
I/O174
GND
I/O175
I/O176
I/O87 I/O177 91
I/O88 I/O178 92
I/O57 I/O89 I/O179 93
I/O58 I/O90 I/O180 94
GND
VCC(1)
I/O181
I/O182
I/O59 (TD2) I/O91 (TD2) I/O183 (TD2) 48 45 65 95
I/O60 (TD1) I/O92 (TD1) I/O184 (TD1) 49 46 66 96
I/O185
I/O186
GND
I/O187
I/O188
I/O61 I/O93 I/O189 67 97
I/O62 I/O94 I/O190 68 98
I/O63 (TD0) I/O95 (TD0) I/O191 (TD0) 50 47 69 99
I/O64, GCK4 I/O96, GCK4 I/O192, GCK4 51 48 70 100
GND GND GND 52 49 71 101
CON CON CON 53 50 72 103
East Side
VCC(1) VCC(1) VCC(1) 54 51 73 106
RESET RESET RESET 55 52 74 108
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
155
PE0 PE0 PE0 56 53 75 109
PE1 PE1 PE1 57 54 76 110
PD0 PD0 PD0 77 111
PD1 PD1 PD1 78 112
GND
VCC(1)
GND
PE2 PE2 PE2 58 55 79 113
PD2 PD2 PD2 56 80 114
GND
No Connect No Connect No Connect 81 119
PD3 PD3 PD3 82 120
PD4 PD4 PD4 83 121
VCC(1) VCC(1)
PE3 PE3 PE3 59 57 84 122
CS0, Cs0n CS0, Cs0n CS0, Cs0n 60 58 85 123
GND
GND
VCC(1)
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
156
SDA SDA SDA 124
SCL SCL SCL 125
GND
PD5 PD5 PD5 59 86 126
PD6 PD6 PD6 60 87 127
PE4 PE4 PE4 61 61 88 128
PE5 PE5 PE5 62 62 89 129
VDD(2) VDD(2) VDD(2) 63 63 90 130
GND GND GND 64 64 91 131
PE6 PE6 PE6 65 65 92 132
PE7 (CHECK) PE7 (CHECK) PE7 (CHECK) 666693133
PD7 PD7 PD7 67 94 134
INTP0 INTP0 INTP0 95 135
GND
VCC(1)
GND
GND
XTAL1 XTAL1 XTAL1 67 68 96 138
XTAL2 XTAL2 XTAL2 68 69 97 139
VDD(2) VDD(2)
RX0 RX0 RX0 98 140
TX0 TX0 TX0 99 141
GND GND GND 100 142
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
157
GND
INTP1 INTP1 INTP1 145
INTP2 INTP2 INTP2 146
GND
VCC(1)
TOSC1 TOSC1 TOSC1 69 70 101 147
TOSC2 TOSC2 TOSC2 70 71 102 148
GND
RX1 RX1 RX1 103 149
TX1 TX1 TX1 104 150
D0 D0 D0 71 72 105 151
INTP3 (CSOUT) INTP3 (CSOUT) INTP3 (CSOUT) 72 73 106 152
CCLK CCLK CCLK 73 74 107 153
VCC(1) VCC(1) VCC(1) 74 75 108 154
I/O65:95 Are
Unbonded(3)
I/O97:144 Are
Unbonded(3)
I/O193:288 Are
Unbonded(3)
North Side
Testclock Testclock Testclock 75 76 109 159
GND GND GND 76 77 110 160
I/O97 (A0) I/O145 (A0) I/O289 (A0) 77 78 111 161
I/O98, GCK7 (A1) I/O146, GCK7 (A1) I/O290, GCK7 (A1) 78 79 112 162
I/O99 I/O147 I/O291 113 163
I/O100 I/O148 I/O292 114 164
I/O293
I/O294
GND
I/O295
I/O296
I/O101 (CS1, A2) I/O149 (CS1, A2) I/O297 (CS1, A2) 79 80 115 165
I/O102 (A3) I/O150 (A3) I/O298 (A3) 80 81 116 166
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
158
I/O299
I/O300
VCC(1)
GND
I/O104 I/O151 I/O301 Shorted to
Testclock
Shorted to
Testclock
Shorted to
Testclock
Shorted to
Testclock
I/O152 I/O302
I/O103 I/O153 I/O303 117 167
I/O154 I/O304 168
I/O305
I/O306
GND
I/O307
I/O308
I/O155 I/O309 169
I/O156 I/O310 170
I/O311
I/O312
GND GND GND 118 171
I/O105 I/O157 I/O313 119 172
I/O106 I/O158 I/O314 120 173
I/O159 I/O315
I/O160 I/O316
VCC(1) VCC(1)
I/O317
I/O318
GND
I/O319
I/O320
I/O321
I/O322
I/O323
I/O324
GND
VCC(1)
I/O107 (A4) I/O161 (A4) I/O325 (A4) 81 82 121 174
I/O108 (A5) I/O162 (A5) I/O326 (A5) 82 83 122 175
GND
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
159
I/O163 I/O327 176
I/O164 I/O328 177
I/O109 I/O165 I/O329 84 123 178
I/O110 I/O166 I/O330 85 124 179
GND
I/O331
I/O332
I/O333
I/O334
I/O111 (A6) I/O167 (A6) I/O335 (A6) 83 86 125 180
I/O112 (A7) I/O168 (A7) I/O336 (A7) 84 87 126 181
GND GND GND 1 88 127 182
VDD(2) VDD(2) VDD(2) 2 89 128 183
I/O113 (A8) I/O169 (A8) I/O337 (A8) 3 90 129 184
I/O114 (A9) I/O170 (A9) I/O338 (A9) 4 91 130 185
I/O339
I/O340
I/O341
I/O342
GND
I/O115 I/O171 I/O343 92 131 186
I/O116 I/O172 I/O344 93 132 187
I/O173 I/O345 188
I/O174 I/O346 189
I/O117 (A10) I/O175 (A10) I/O347 (A10) 5 94 133 190
I/O118 (A11) I/O176 (A11) I/O348 (A11) 6 95 134 191
VCC(1)
GND
I/O349
I/O350
I/O351
I/O352
I/O353
I/O354
GND
I/O355
I/O356
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
160
Notes: 1. VCC is I/O high voltage.
2. VDD is core high voltage.
3. Unbonded pins are No Connects.
VDD(2) VDD(2)
I/O177 I/O357
I/O178 I/O358
I/O119 I/O179 I/O359 135 192
I/O120 I/O180 I/O360 136 193
GND GND GND 137 194
I/O361
I/O362
I/O181 I/O363 195
I/O182 I/O364 196
I/O365
I/O366
GND
I/O367
I/O368
I/O121 I/O183 I/O369 197
I/O122 I/O184 I/O370 198
I/O123 (A12) I/O185 (A12) I/O371 (A12) 7 96 138 199
I/O124 (A13) I/O186 (A13) I/O372 (A13) 8 97 139 200
GND
VCC(1)
I/O373
I/O374
I/O375
I/O376
I/O377
I/O378
GND
I/O187 I/O379
I/O188 I/O380
I/O125 I/O189 I/O381 140 201
I/O126 I/O190 I/O382 141 202
I/O127 (A14) I/O191 (A14) I/O383 (A14) 9 98 142 203
I/O128, GCK8 (A15) I/O192, GCK8 (A15) I/O384, GCK8 (A15) 10 99 143 204
VCC(1) VCC(1) VCC(1) 11 100 144 205
Table 47. AT94K Pin List (Continued)
AT94K05
96 FPGA I/O
AT94K10
192 FPGA I/O
AT94K40
384 FPGA I/O
Packages
PC84 TQ100 PQ144 PQ208
AT94K Family
161
Ordering Information
Usable Gates Speed Grade Ordering Code Package Operation Range
5,000 -25 MHz AT94K05AL-25AJC
AT94K05AL-25AQC
AT94K05AL-25BQC
AT94K05AL-25DQC
84J
100Q
144Q
208Q
Commercial
(0°C - 70°C)
AT94K05AL-25AJI
AT94K05AL-25AQI
AT94K05AL-25BQI
AT94K05AL-25DQI
84J
100Q
144Q
208Q
Industrial
(-40°C - 85°C)
10,000 -25 MHz AT94K10AL-25AJC
AT94K10AL-25AQC
AT94K10AL-25BQC
AT94K10AL-25DQC
84J
100Q
144Q
208Q
Commercial
(0°C - 70°C)
AT94K10AL-25AJI
AT94K10AL-25AQI
AT94K10AL-25BQI
AT94K10AL-25DQI
84J
100Q
144Q
208Q
Industrial
(-40°C - 85°C)
40,000 -25 MHz AT94K40AL-25BQC
AT94K40AL-25DQC
144Q
208Q
Commercial
(0°C - 70°C)
AT94K40AL-25BQI
AT94K40AL-25DQI
144Q
208Q
Industrial
(-40°C - 85°C)
Package Type
84J 84-lead, Plastic J-leaded Chip Carrier (PLCC)
100Q 100-lead, Thin (1.0 mm) Plastic Quad Flat Package (TQFP)
144Q 144-lead, Plastic Gull Wing Quad Flat Package (PQFP)
208Q 208-lead, Plastic Gull Wing Quad Flat Package (PQFP)
AT94K Family
163
Packaging Information
1.158(29.4)
1.150(29.2)
1.195(30.4)
1.185(30.1)
0.0125(0.318)
0.0075(0.191)
0.021(0.053)
0.013(0.330)
1.00 REF SQ
SQ
.032(.813)
.026(.660)
SQ
.050(1.27) TYP
.045 X 45˚
PIN NO. 1
IDENTIFY
.045(1.14) X 30˚ - 45˚
1.13(38.7)
1.09(27.7)
.120(3.05)
.090(2.29)
.020(0.51) MIN
.180(4.57)
.165(4.19)
.020(0.51) X 45˚ MAX (3X)
*Controlling dimension: millimeters
PIN 1 ID
0.50 BSC
16.00(0.630) BSC
0.27(0.011)
0.17(0.007)
14.00(0.551) BSC
0.15(0.006)
0.05(0.002)
0.75(0.030)
0.45(0.018)
0-7
0.20(0.008)
0.10(0.004)
1.05(0.041)
0.95(0.037)
*Controlling dimension: millimeters
0.50 BSC
0.20(0.008)
0.10(0.004)
0.45(.018)
0.75(.030)
1.45(0.057)
1.35(0.053)
0.05(0.002)
0.15(0.006)
20.00(0.787) BSC
0.17(0.007)
0.27(0.011)
22.00(0.866) BSC
PIN 1 ID
0-7
PIN 1 ID
.157(3.97)
.127(3.22)
1.204(30.60) BSC
.020(0.50) BSC
.017(0.43)
.027(0.69)
.020(0.50)
.002(0.05)
0.45(1.14)
0.75(1.91)
.008(0.20)
.004(0.10)
10
0
1.102(28.00) BSC
84J, 84-lead, Plastic J-leaded Chip Carrier (PLCC)
Dimensions in Inches and (Millimeters)
JEDEC STANDARD MS-018 AF
100Q, 100-lead, Thin (1.0 mm) Plastic Quad Flat
Package (TQFP)
Dimensions in Millimeters and (Inches)*
JEDEC STANDARD MS-026 AED
144Q, 144-lead, Plastic Gull Wing Quad Flat
Package (PQFP)
Dimensions in Millimeters and (Inches)*
JEDEC STANDARD MS-026 BFB
208Q, 208-lead, Plastic Gull Wing Quad Flat
Package (PQFP)
Dimensions in (Millimeters) and Inches
JEDEC STANDARD MS-029 FA-1
Drawings for general information only. Use specifications from JEDEC standards.
AT94K Family
164
-
Thermal Coefficient Table
Package Style Lead Count
Theta J-A
0 LFPM
Theta J-A
225 LFPM
Theta J-A
500 LPFM Theta J-C
PQFP 144 33 27 23 8.5
PQFP 208 32 28 24 10
TQFP 100 47 39 33 22
PLCC 84 37 30 25 12
© Atmel Corporation 2001.
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