CDB6420 Cirrus Logic Inc, CDB6420 Datasheet - Page 14

• Manufacturer Part Number: CDB6420
• Description: Development Kit
• Manufacturer: Cirrus Logic Inc

Specifications of CDB6420

• Silicon Manufacturer: Cirrus Logic
• Application Sub Type: Speakerphone
• Kit Application Type: Audio / Video / TV
• Silicon Core Number: CS6420
• Kit Contents: Board
• Kit Features: Analog And Digital Patch Area
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Register 1
HD - Half-Duplex Disable
In normal operation, the CS6420 will be in a half-
duplex mode if the echo canceller is not providing
enough loop gain reduction to prevent howling.
This half-duplex mode would be active at power-
up, for example, before the adaptive filter has had a
chance to adapt. This half-duplex mode prevents
howling and also masks the convergence process.
In some cases, such as when measuring conver-
gence speed (see Testing Issues), the half-duplex
14
b15
HD
13-12
11-10
Bits
0
9-5
4-3
15
14
RSD
b14
* Denotes reset value
0
RGain
Name
Taps
NCC
RSD
b13
TVol
HD
Taps
10
b12
AEC/NEC Tap Allocation
b11
Rx Suppression Disable
NEC Coefficient Control
Half-Duplex Disable
NCC
Tx Volume Control
00
Rx Analog Gain
b10
Function
Table 4. Register 1 Bit Definitions
b9
b8
01010
TVol
b7
mode is undesirable. By default, the half-duplex
mode is enabled.
RSD - Receive Suppression Disable
The Receive Supplementary Echo Suppression
function is a non-linear echo control mechanism.
Supplementary Echo Suppression attenuates sig-
nals in the receive direction by 24 dB when far-end
speech is absent in the receive path. The attenua-
tion is released only when the receive channel is ac-
tive. It is also designed to not be triggered by
b6
01010*
00000
00001
00100
01011
11101
11110
11111
Word
10*
00*
00*
00
01
11
01
10
11
01
10
11
---
---
---
0*
0*
1
1
b5
b4
RGain
00
444/0 (55.5ms/disabled)
380/128 (47.5ms/16ms)
316/192 (39.5ms/24ms)
252/256 (31.5ms/32ms)
disable Rx suppression
enable Rx suppression
b3
disable half-duplex
enable half-duplex
Operation
reserved
Normal
+30 dB
+27 dB
+18 dB
Freeze
b2
-57 dB
-60 dB
9.5 dB
+0 dB
12 dB
0
0
Clear
-3 dB
mute
0 dB
6 dB
CS6420
b1
1
1
DS205PP2
b0
0
0