CS6422

3

3.5.4 HDly - Half-Duplex Holdover Delay......................................................................... 19

3.5.5 HHold - Hold in Half-Duplex on Howl ...................................................................... 19

3.5.6 TDSRmp - Tx Double-talk Suppression Ramp rate ................................................ 19

3.5.7 RDSRmp - Rx Double-talk Suppression Ramp rate ............................................... 20

3.5.8 IdlTx - half-duplex Idle return-to-Transmit ............................................................... 20

3.6 Register 3 ......................................................................................................................... 21

3.6.1 TSAtt - Transmit Suppression Attenuation.............................................................. 22

3.6.2 PCSen- Path Change Sensitivity ............................................................................ 22

3.6.3 TDbtS - Tx Double-talk Suppression attenuation.................................................... 22

3.6.4 RDbtS - Rx Double-talk Suppression attenuation ................................................... 22

3.6.5 TSThd - Transmit Suppression Threshold .............................................................. 22

3.6.6 TSBias - Transmit Suppression Bias ...................................................................... 22

3.7 Register 4 ......................................................................................................................... 23

3.7.1 AErle - AEC Erle threshold...................................................................................... 24

3.7.2 AFNse - AEC Full-duplex Noise threshold .............................................................. 24

3.7.3 NErle - NEC Erle threshold ..................................................................................... 24

3.7.4 NFNse - NEC Full-duplex Noise threshold.............................................................. 24

3.7.5 RGain - Receive Analog Gain ................................................................................. 24

3.7.6 TGain - Transmit Analog Gain ................................................................................ 24

3.8 Register 5 ......................................................................................................................... 25

3.8.1 HwlD - Howl detector Disable ................................................................................. 26

3.8.2 TD - Tone detector Disable ..................................................................................... 26

3.8.3 APCD - Acoustic Path Change detector Disable .................................................... 26

3.8.4 NPCD - Network Path Change detector Disable..................................................... 26

3.8.5 APFD/NPFD - Acoustic Pre-emphasis Filter Disable/Network

Pre-emphasis Filter Disable..................................................................................... 26

3.8.6 AECD - Acoustic Echo Canceller Disable ............................................................... 27

3.8.7 NECD - Network Echo Canceller Disable ............................................................... 27

3.8.8 ASdt - Acoustic Sidetone level ................................................................................ 27

3.8.9 NSdt - Network Sidetone level ................................................................................ 27

3.9 Reset ............................................................................................................................... 28

3.9.1 Cold Reset .......................................................................................................... 28

3.9.2 Warm Reset ........................................................................................................ 28

3.9.3 Reset Timer ........................................................................................................ 28

3.10 Clocking ......................................................................................................................... 28

3.11 Power Supply ................................................................................................................ 29

3.11.1 Power Down Mode ............................................................................................ 29

3.11.2 Noise and Grounding ........................................................................................ 29

4. DESIGN CONSIDERATIONS ................................................................................................. 31

4.1 Algorithmic Considerations .............................................................................................. 31

4.1.1 Full-Duplex Mode ................................................................................................ 31

4.1.1.1 Theory of Operation ........................................................................... 31

4.1.1.2 Adaptive Filter ..................................................................................... 32

4.1.1.2.1 Pre-Emphasis ............................................................................ 32

4.1.1.2.2 Graded Beta .............................................................................. 33

4.1.1.3 Update Control .................................................................................... 33

4.1.1.4 Speech Detection ................................................................................ 33

4.1.2 Half-Duplex Mode ............................................................................................... 34

4.1.2.1 Idle Return to Transmit ....................................................................... 34

4.1.3 AGC .................................................................................................................... 34

4.1.4 Suppression ........................................................................................................ 35

4.1.4.1 Transmit Suppression ......................................................................... 36

4.1.4.2 Receive Suppression .......................................................................... 36

CS6422

DS295F1

3