ML7204-003 datasheet(41/214 Pages) LAPIS

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FEDL7204-003-02

ML7204-003

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A-3. G.711 (

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

Figure 24 Speech CODEC Coding Format Switching Control Method on the

Transmit 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 16 G.711

(

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

 Switching processing

Switch the Speech CODEC coding format from G711 to G.729.A within the valid MCU read period according

to the setting in the Speech CODEC selection register on the transmit side (TX_SCSEL[1:0]). When the

switching of the Speech CODEC coding format is detected, the LSI internal section discards the data currently

being encoded (T6 encoding data in the example shown above) and starts encoding in the G.729.A coding

format from the next frame.

A read request is issued normally by FR0B also for the frame where coding format has been switched;

however, a transmit error (TXERR_CH1 = “1”) does not occur even if data read processing does not terminate

within the valid read period. If a transmit error occurred before this frame, that transmit error is cleared to

“0” at termination of this frame.

(Note)

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

 G.711 switching

processing may be delayed by one frame. Therefore, check if the transmit request is for the data encoded in

the G.729.A or encoded in the G.711 coding format by referencing the transmit Speech CODEC operation

mode notification flag (TX_SCFLAG) when requesting transmission due to the fall of FR0B.

 G.729.A operation (after switching)

Operates according to the contents that are described in Operation and Error processing in Figure 14

G.729.A transmit buffer control method at single-channel operation (10 ms frame mode).

FR0B

(Pin output)

MCU read

Valid read section

RE4

RE5

Speech

CODEC

ENC

10 ms

T5(G.711)

T6(G.711)

 G.711 operation (before switching)

 Switching processing

 G.729.A operation (after switching)

FR0_CH1

INTB

(Pin output)

Valid read section

Init

T7(G.729.A)

T8(G.729.A)

T9(G.729.A)

RE7

RE8

FR0B

(Pin output)

MCU read

Speech

CODEC

ENC

10 ms

FR0_CH1

INTB

(Pin output)

G.711

G.729.A

Transmit SC coding

format setting

TX_SCSEL[1:0]

G.711

G.729.A

Transmit SC operation

mode notification

TX_SCFLAG

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