AT2004 datasheet(7/25 Pages) ETC1

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AT2004

4 Channels ADPCM Processor with Echo Cancellation and Conferencing

Page 7 of 25

Chip ID Setup

The two Chip ID pins A0 and A1 (Pins 6,7) should also be set during chip initialization. The “Chip ID” is used to differentiate between

AT2004 chips in a system that uses more than one AT2004 chip. When using only one chip, it is recommended to tie A0 and A1 to

digital zero. Thus, when programming the AT2004 chip, you can use the Chip ID = ‘00’ to substitute wherever you see A1, A0.

The maximum number of AT2004 can be used in a system is 4, and a chip ID must be assigned to each AT2004 in a system. The format

of A0 and A1 should be specified according to the following table:

Description

AT2004 chip ID=0

AT2004 chip ID=1

AT2004 chip ID=2

AT2004 chip ID=3

Programming the AT2004

Using the Serial Port to Input Commands

Commands for the AT2004 are entered using the 3-wire Serial Interface. The “three wires” refer to the three pins which control the

interface: SDI/SDO (Serial Data In/Serial Data Out), SCLK (Serial Clock), and SCSZ (Serial Chip Select). When SCSZ is enabled (low),

the SDI is sampled every SCLK signal. Sampled bits are collected into an 8-bit register and read by the DSP. The SCSZ signal can be

held more than 8-bits at a time in 8-bit multiples forming a COMMAND SEQUENCE. Different command sequences form the bulk of

AT2004 programming.

Byte 1

SDI

SCLK

SCSZ

Generic 3-byte Command Sequence

LSB B1

Byte 2

Byte 3

Command Sequence Overview

The AT2004 understands five different types of command sequences.

The PLL command sequences sets the operating speed of the chip.

The MCU7byte command sequence set the ADPCM algorithms, bit-slots, delay and EC’s reference channel number.

The Per Channel Control command sequence sets the echo canceling options and other options in the chip.

The Conferencing command sequence sets the conferencing channels.

AT2004 Datasheet(PDF) 7 Page - List of Unclassifed Manufacturers