AT2004
4 Channels ADPCM Processor with Echo Cancellation and Conferencing
Page 1 of 25 ©2001 Atelic System, Inc

Atelic Systems, Inc.

AT2004 Application Note Preliminary
4 Channels ADPCM Processor with Echo Cancellation and Conferencing
Version 1.0 January 29, 2001
Description

The AT2004 is a four full-duplex channels, ADPCM processor with conferencing and echo cancellation capabilities. It
follows the G.726 ITU Standard for ADPCM compression for 40k, 32k, 24k and 16k bitrates with selectable µ-law and A-
law input/output. It conforms to ITU G.165/G.168 Digital Adaptive Echo Canceller specification for line echo delay up to
20ms. Using the command serial interface, each individual half-channel can be independently configured for ADPCM,
conferencing and echo canceling features.

Features

• 4 full channels of ITU G.726 ADPCM
• 4 full channels of ITU G.165/G.168 complia nt echo cancellation with up to 20ms echo delay
• Fast and robust convergence for adaptive echo canceller, even in the presence of background noise
• Nonlinear processing with adaptive suppression threshold and comfort noise generation for echo canceller
• Per channel selectable µ-Law and A-law input/output
• On-chip time slot assignment
• Available internal clock generator and frame sync. generator
• Simple 3-wire serial command port for chip configuration
• Conferencing capabilities for up to 3 additional sound sources

Applications

• DECT
• VoIP / VoDSL
• Wireless telephone systems
• Wireless PBX systems

Default Settings

• 4 channels of µ-law PCM input on Xin in time slot 0, 1, 2, 3
• 4 channels of the corresponding ADPCM output at 32kbps on Xout in time slot 0, 1, 2, 3
• 4 channels of ADPCM input at 32kbps on Yin in time slot 0, 1, 2, 3
• 4 channels of corresponding PCM µ-law output on Yout in time slot 0, 1, 2, 3
• Echo cancellation enabled for four channels
• Conferencing disabled

Note: To change the default settings, commands could be sent through the 3-wire interface.