CDB6420 Просмотр технического описания (PDF) - Cirrus Logic

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CDB6420

Full-Duplex Speakerphone Chip

Cirrus Logic 

CS6420

Register 1

b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0

HD RSD

0

0

Taps

10

NCC

00

TVol

01010

RGain

00

0

1

0

0

1

0

Bits

Name

15

HD

14

RSD

13-12

Taps

Function

Half-Duplex Disable

Rx Suppression Disable

AEC/NEC Tap Allocation

11-10

NCC

NEC Coefficient Control

9-5

TVol

Tx Volume Control

4-3

RGain

Rx Analog Gain

Word

0*

1

0*

1

00

01

10*

11

00*

01

10

11

00000

00001

---

00100

---

01010*

01011

---

11101

11110

11111

00*

01

10

11

Operation

enable half-duplex

disable half-duplex

enable Rx suppression

disable Rx suppression

444/0 (55.5ms/disabled)

380/128 (47.5ms/16ms)

316/192 (39.5ms/24ms)

252/256 (31.5ms/32ms)

Normal

Clear

Freeze

reserved

+30 dB

+27 dB

+18 dB

+0 dB

-3 dB

-57 dB

-60 dB

mute

0 dB

6 dB

9.5 dB

12 dB

* Denotes reset value

Table 4. Register 1 Bit Definitions

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

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

14

DS205PP2

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