ML7204-003 datasheet(46/214 Pages) LAPIS

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FEDL7204-003-02

ML7204-003

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B-3. G.711 (

-law and A-law)  G.729.A switching control (10 ms frame mode)

Figure 28 Speech CODEC Coding Format Switching Control Method on the

Receive Side G.711

G.729.A<10 ms frame mode>

 G.711 operation (before switching)

Operates according to the contents described in Operation and Error processing in Figure 20 G.711

(

-law and A-law) receive buffer control method at single-channel operation (10 ms/frame mode).

 Switching processing

Switch the Speech CODEC coding format from G.711 to G.729A within the valid MCU write period

according to the setting in the Speech CODEC selection register on the receive side (RX_SCSEL[1:0]).

When receive data is written from the MCU in the frame from which the switching of the Speech CODEC

coding format has been detected, the LSI internal section performs decoding processing in the next frame.

When receive data is not written from the MCU, data is generated according to the PLC algorithm and then

output (silent output when the PLC function is disabled) in the next frame; however, a receive error

(RXERR_CH = “1”) does not occur.

If a receive error occurred before this frame, that receive error is cleared to “0” at termination of this frame.

To avoid a sudden transition from a voice state to a silent state, the function that gradually attenuates the

decoding output (fade-out function) operates.

(Note)

If the coding format is switched outside of the valid MCU write period, the G.729.A

 G.711 switching

processing may be delayed by one frame. Therefore, check whether the receive request is for the receive

data encoded in the G.729.A or encoded in the G.711 by referencing the receive Speech CODEC operation

mode notification flag (RX_SCFLAG) when requesting reception due to the fall of FR1B.

 G.729.A operation (after switching)

Operates according to the operation that is effective on and after the second receive request that is described in

Operation and Error processing in Figure 18 G.729.A receive buffer control method at single-channel

operation (10 ms/ frame mode).

To avoid a sudden transition from a silent state to a voice state, the function that gradually amplifies the

decoding output of the receive data that was initially written from MCU (fade-in function) operates.

FR1B

(Pin output)

MCU write

Valid write section

Speech

CODEC

10 ms

WE_SC7

WE_SC8

 G.711 operation (before switching)

 Switching processing

 G.729.A operation (after switching)

FR1

INTB

(Pin output)

R5(G.711)

R6(G.711)

R7(G.711)

R8(G.711 or silent)

Fade-out function valid period (*1)

R5(G.711)

R6(G.711)

R7(G.711)

R8(G.711 or PLC)

Fade-out function valid period (*1)

DEC

OUT

PLC_EN=1

PLC_EN=0

MCU write

Valid write section

FR1B

(Pin output)

10 msec

Speech

CODEC

DEC

OUT

WE_SC10

WE_SC11

WE_SC12

WE_SC13

WE_SC14

R10(G.729.A)

R11(G.729.A)

R12(G.729.A)

Silent

Fade-in function valid period(*1)

Approx. 20 ms

(*1) Fade-in/fade-out function valid period: Approx. 15 ms

FR1

INTB

(Pin output)

Silent

G.711

G.729.A

Receive SC coding

format setting

RX_SCSEL[1:

G.711

G.729.A

Receive SC

operation mode

notification

RX_SCFLA

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