AT75C110 - Atmel Corporation - Datasheet.Support

Features

•10 MIPS Flash-based AVR® Core Microcontroller

•High Efficiency Compression (4.5 kbps)

•Automatic Timestamp

•Full Duplex Handsfree Support

•Line and Acoustic Echo Cancellation

•DTMF Generation and Detection

•Call Progress Tone Detection

•Caller ID and Alert Tone Detection

•Power Management and Monitoring

•2 On-chip Voice Codecs for Line and User Sides

•Programmable Equalizer and AGC

•On-chip 100 mW Audio Amplifier

•General Purpose UART

•DataFlash™ Controller for Mass Storage and Voice Prompt

•LCD Display Controller

•K e y board Controller

•User-defined I/Os

Description

The Atmel AT75C110 integrated circuite (IC) provides a cost-effective solution for

embed ded or stan dalone message recording applicat ions. It p rovides th e syste m

developer with a comprehensive set of programmable DSP algorithms, thus spanning

the range of applications from simple voice recorder to full-fledged smartphone with

display, handsfree features and answering capabilities.

The chip is built around the AVR microcontroller (MCU) architecture. The application

program resides in an on-chip Flash program memory. During the boot stage, this

memory is p rogrammed throug h th e on-ch ip UART from any software develo pment

platform. The AVR MCU core controls all the on-chip peripherals and supports the

user interface. The main peripheral is the programmable DSP unit.

The DSP unit provides the system with a set of processing facilities widely used in

voice recording and telephone applications. It is controlled by the application software

throug h predefined s ystem reques ts. The DSP unit i s connected di rectly to the l ine

side and acoustic voice c odecs and to the DataFlash mass storage memory. This

structure allows the DSP unit to work as a standalone co-processor, while the applica-

tion software performs other system tasks.

The DSP uni t features an Atm el pr oprietar y voic e comp ressi on algo rithm whi ch leads

to a bit rate as low as 4.5 kb ps. This gi ves a good compromise between me mory

requireme nts and qua lity du ring playbac k. At that sp eed, a seria l 8M bytes DataFl ash

can hold up to 30 minutes of voice messages. This low pincount memory can be glue-

lessly connected to the AT75C110.

Furthermore, the AT75C110 supports advanced telephone features, such as hands-

free o perati on w ith echo ca ncell ation , ton e ha ndli ng ( DTMF, calle r I D, al ert , etc .) an d

correction for low-cost microphones and speakers.

Rev. 1073AS–A–07/98

Digital

Te lephone

Ans weri ng

Device

AT75C110

Ad v ance

Information

AT75C110

AT75C110 Block Diagram

Applicatio n Example: Full Duplex Speakerphone with Answering Functions

Line-side

Codec User-side

Codec

DataFlash

controller

I/O Port

LCD

Controller

Keyboard

Controller

DSP Request

Controller

Program Flash

RAM

Real Time

Clock

UART

Power

Management

Clocks

Generation

Phone

Line

General

Purpose

I/O

Display

Keyboard

Speaker

Headphones

Mic 1

Mic 2

DataFlash

Memory

PCM I/O PCM I/O

Rx/Tx

Power Sense

16 MHz

System

Oscillator

32768 Hz

RTC

Oscillator

External

50/60 Hz

Clock Source

DSP Unit

AVR Core

DataFlash

Line SLIC AT75C110

Handset

Display Keyboard

Handsfree

AT75C110

Functional Description

AVR Microcontroller Core

The AVR MC U core is based on an enhanc ed RISC arc hi-

tect ure that co mbines a ri ch inst ruction s et with 32 gen eral

purpose wor king reg ist ers . A ll 32 regis te rs a re di re ct ly c on-

nected to the Ar it hm etic and Logi c Uni t (A LU), al low ing two

indep ende nt regi st er s to be acce sse d in on e si ngl e in str u c-

tion executed in one cycle. The resulting architecture is

more c ode efficien t while ac hieving th roughputs up to te n

times faster than conventional CISC microcontrollers.

More detailed information on the AVR MCU Core is avail-

able in the Atmel AVR Core Datasheet and the Atmel AVR

Microcontroller Databook.

DSP Unit

The DSP Unit is a programmable functional block which

performs all the voiceband calculations in a configurable

way. Several algorithms can run in paralle l, with few restric-

tions.

The DSP Unit is programmed by the application software

run by t he AVR core throu gh com mand m essa ges. A com-

mand message is a set of codes made of one opcode fol-

lowed by zero or more parameters.

When a special event occurs in the da ta processin g (eg

valid D TMF c ode de tected), the DS P Uni t has the ab ility t o

elaborate a status message and to post it to the application

software.

The c omprehens ive comm and and status message set is

fully explained in the detailed datasheet.

Below is an overview of the main available algorithms. If

several algorithms are to be run in parallel, there must be a

separate command message for each of them. If the DSP

Unit receives several incompatible command messages

(e.g. a message requests DTMF detection and another

reques ts DTMF generation ), only the last one will be take n

into account. Command messages with an undefined

opcode are not processed.

Voice Compression

The DSP Unit’s main task is to process in real time voice

compres sion and d ecompress ion. Based o n a prop rietary

algorithm, the speech compression ratio enables up to 30

minutes of voice to be stored in an 8M-bit memory. The

high efficiency of the algorithm allows other tasks required

in a smart phone application to run in parallel.

Message Playback

Controlled by the AVR microcontroller, the playback pro-

cess is handle d by the DS P unit fo r speech decompres-

sion, and by the AVR for memory management, leaving the

AVR free for other control tasks. The application pr ogram-

mer can use these resources to feature a user-friendly

access to messages.

Line Echo Cancellation

The AT75C110 contains a line echo cancellation unit to

eliminate near end echo. This unit is based on an adapta-

tive F IR filter whic h computes the expected echo, and a

subtr actor whi ch remove s it from the tr ansmitted s ignal.

Since the echo characteristics can slowly vary with time, an

adaptativ e al gor ithm contin uous ly up date s th e ec ho mo del .

The line echo canceller is programmable, and is useful dur-

ing tone detection.

A block diagram of the line echo canceller is shown below.

Acoustic Echo Cancellation

The AT75C110 con tains an ac oustic ec ho canc ellation uni t

to eliminate the interaction of the microphone and the

speaker. It is based on an adaptative FIR structure, as

shown in the figure below:

DTMF Generation

The DSP Unit provid es an efficie nt way to genera te sine-

wave tones , or the su m of tw o sinewav e tones . The gene r-

ated sig nal ha s l ow distortion, and the fr eq uenc y res olu tio n

is less th an 1 Her tz . The typi ca l a ppl ic ati on o f ton e ge ner a-

tion is DTMF generation, but custom tones can also be

emitted.

Line In

Line Out

Adaptative algorithm FIR Other

processing

algorithms

Mic

Speaker

Adaptative algorithm

FIR

Other

processing

algorithms

AT75C110

The tone generation command message has four parame-

ters: th e frequency co ntrol word for th e first tone, the f re-

quency control word for the second tone, the tone duration,

and tone separation duration.

To improve the DTMF detection by the receiver, the hand-

set and handsfree microphone signals can be disabled dur-

ing tone and tone separation.

DTMF Detect ion

The DTMF codes detector is enabled by a special com-

mand message. This message has several parameters,

includ ing minimum ton e duration a nd frequency a ccuracy

around nominal values.

When a val id cod e is dete cted, the DSP Unit can gener ate

an interrupt to the AVR Core and deliver the detected

value.

All sixteen standard DTMF codes are recognized.

Calling Tone Detection

When a datacom device (e.g. modem or fax machine) dials

a number, it sends a calling tone as soon as the whole

number is comp letely d ialed. Thi s enable s the r eceiver t o

distinguish datacom from voice calls.

The DSP Unit has the ability to detect the standard calling

tones.

Call Progress Tone Detection

The AT75C 110 ca n detect cal l progress to nes. This func-

tion is programmable for tone duration, tone separation

duration and some other parameters. When it has detected

a programmable number of tone/tone separation, it can

send an inter rupt to the AVR Cor e to inform the app lica tion

of the call progress.

Alert Tone Detection

The alert tone is a part of the caller ID protocol. W hen the

alert tone detector is enabled, an interrupt is triggered to

the AVR Core to inform the application so ftware that the

caller ID detector can be enab led. The alert to ne detector

can be configured by several parameters, including the

accuracy around the nominal frequencies.

Caller ID Detection

The caller ID protocol is based on a 1200 bps FSK modula-

tion. When the call er ID detector is enabled , it can deliver

the demodulated deserialized data to the appli cation soft-

ware. This software has the responsibility to interpret the

data. Several parameters can control the way demodula-

tion is performed.

Microphone and Speaker Equalization

Two equal iz ing f il ters ar e pl ac ed i n ser i es wi th the a co us tic

side codec. These filters can be used to correct the fre-

quency response of low-cost microphones and speakers.

Other Features

DSP Auxiliaries

The DSP Unit has a number of auxiliary features, such as

AGC for an alo g si gna ls , dig ita l v olu me c ontr ol , or thre shol d

detection for various signals.

Keyboard Controller

The embed ded keyboard contr oller has t he required l ogic

to allow direct connection of a low-cost, 16-key matrix key-

board. Thi s logic include s debou ncing, scan fram es gener-

ation and interrupt generation.

When the AVR Core is interrupted, it just has to read a reg-

ister which holds the code of the pushed key.

LCD Controller

The AT75C110 features an on-chip generic LCD controller.

To allow flexibility regarding the wide range of available

LCD displays, the controll er does not include the analog

drivers. It provides the system with a bus dedicated to dis-

play devic es. This bus is fully configurable and su pports

most of the standard device interfaces.

I/O Port

The primary goal of the four bidirectional I/Os is the phone

line in terfac e co ntrol . In a typic al a nswer ing m achin e appl i-

cation, o ne I/O is connect ed to the rin g detect ( input) and

another c ontrols the hook-up ( output). Howev er, they can

also be used as general purpose I/Os (LED control, hand-

set switch detect, etc.).

Real Time Clock

The real time clock holds the current date and time needed

for the me ssage time stamp. The time bas e can be der ived

from ei ther the on -chip 327 68 Hz os cillator or an exter nal

50 Hz or 60 Hz source.

This s tructure takes advanta ge of th e high, long-ter m fre-

quency ac curacy of the main’s AC supply . Should the AC

supply dis appear, the RTC source c an be switched to the

crystal source.

Clocks Generator

The Clocks Generato r includes a 16 MHz crystal oscillator

as well as all circuitry needed to derive the various system

clocks from this oscillator.

The additional clock logic also has the responsibility of

managing ov er al l p ower c on su mpt ion v ia a set o f pr o gr am-

mable clock dividers. Thus optimization of power consump-

tion with respect to required processing capabilities of the

chip for a given application is assured.

UART

A general purpose UART is included in the AT75C110. It

can be us ed t o enl ar ge the r an ge o f applica tio ns by p r ovi d-

ing an industry standard communication channel.

AT75C110

The main uses of this UART are application code download

from the software development platform, and message

upload to a PC for backup purposes.

The communication parameters are configurable (speed,

parity, etc.)

Power Management

The Power Management unit is built around a supply volt-

age monitoring device. When a power fail is detected, the

unit can be programmed to trigger special events:

• An inter rup t generati on. The ap plic ation cod e jumps to a

special routine which handles power outage. The

peripherals are put in power down mode and the

message allocation table is written to insure data

consistency before definitive shutdown.

• A switch to low speed clock.

DataFlash Controller

The DataFlash Controller allows a dir ect connection of an

external DataFlash to the AT75C110. There are two infor-

mation flows: a voice flow and a control flow.

The voice flow transports compressed data between the

DSP Unit and the DataFlash. The control flow comes from

the application software which pr ograms the address the

and the data di re ction. This architecture allows the dat a

production/consumption and the memory management

algorithms to be split between the DSP Unit and the appli-

cation software.

Development Tools

AT75APPLI

The AT75C110 will be provided with the AT75APPLI, an

application development system. It is based on the AVR

ICEPRO-ASIC and the AT75C110 development chip. It is a

real time In-Circuit Emulator for any ASIC based on an

AVR Core. It will allow the application de veloper to write,

run and debug the code written for his specific application.

This system is compatible with all s oftware development

tools provided with AVR based products.

The AT75 system contains the following elements :

• AVR ICEPRO-ASIC

• BASEPOD with the AT75C110 development chip

• Pod Cable

• AT75C110 Probe with cable

• RS-232 cable

AT75C110EVAL

The AT75C110EVAL stand-alone evaluation board allows

an evaluation of the acoustic performance and the tele-

phone capabilities of the AT75C110. In addition to the

AT75C110, the boar d con t ains a micr oph one, a s pe ak er, a

keyboard, an LCD display, a phone line interface and a

cable to a PC.