TCM4400 datasheet(51/64 Pages) TI

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TCM4400E

GSM/DCS BASEBAND AND VOICE A/D

AND D/A RF INTERFACE CIRCUIT

SLWS082A – JULY 1999 – REVISED MARCH 2000

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

voiceband uplink control register

The values in the voiceband uplink control register bit positions control not only the power level of the audio in

the uplink path but also set the gain of the PGA from –12 dB to 12 dB in 1 dB steps. Bit MICBIAS and VULMIC

and VULAUX are shifted by one position to the left. This is shown in Table 17.

Table 17. Voiceband Uplink Control Register

VBCTL1: VOICEBAND UPLINK CONTROL REGISTER

ADDRESS: 10

R/W

VDXMUTE

MICBIAS

VULMIC

VULAUX

VULPG4

VULPG3

VULPG2

VULPG1

VULPG0

VULON

1/0

R/W

R /W

R/W

<–ACCESS TYPE

<–VALUE AT RESET

VULON:

Power on the uplink path of the audio codec

VULAUX:

Enables the auxiliary input amplifier if bit VULON is 1

VULMICL:

Enables the microphone input amplifier if bit VULON is 1

MICBIAS:

When MICBIAS = 0, the analog bias for the electret-type microphone and external

decoupling is driven to 2 V; when the value is 1, the bias is 2.5 V.

VDXMUTE:

When VDXMUTE = 1, the VDX output is forced to zero, when the value is 0, VDX is

transmitted normally. To avoid cutting a VDX word during transmission due to

asynchronism of writing this bit via DSP or MCU serial interface, VDXMUTE is internally

resynchronized with the 8 KHz voice frame.

VULPG (0–4):

Gain of the voice uplink programmable gain amplifier (–12 dB to 12 dB in 1 dB step), see

Table 18.

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