Owner manual

AT76C551

1612D–08/01

Voice CODEC

The Voice CODEC has four modes: CVSD, A-law, U-law and pass through where data is

transferred out through the digital interface. The module has independent receive and transmit

paths – each having a dedicated 32-byte FIFO.

VC_CTRL: Voice CODEC Analog Control

addr: 500000 hex R/W 13 bits

• Bits 15..13 – Reserved

• Bit 12 – Rate

1= 64 kHz sampling rate

0= 8 kHz sampling rate

• Bits 11..10 – ADC_TC[1:0]

Type of AD conversion:

00 = Reserved

01 = Reserved

10 = Reserved

11 = Conversion initiated by 64/8 kHz clock

• Bit 9 – ADC_SC

Start conversion

• Bit 8 – ADC_EN: Enables ADC Converter

• Bit 7 – DAC_EN: Enables DAC Converter

• Bit 6 – DIG_INT: Enables Digital Interface

• Bit 5 – AL_DEC: Enables A-law Decoder

• Bit 4 – UL_DEC: Enables U-law Decoder

• Bit 3 – CV_DEC: Enables CVSD Decoder

• Bit 2 – AL_ENC: Enables A-law Encoder

• Bit 1 – UL_ENC: Enables U-law Encoder

• Bit 0 – CV_ENC: Enables CVSD encoder

Note: Default Value: 0000 hex

Before conversions can take place the ADC and the DAC must be powered up. The ADC

requires 10 µs power-up time while the DAC 20 µs power-up time. During this time, the coding

modules must not be enabled. After powering up, the ADC/DAC conversion rate and the

required coding mode can be programmed.

VCDI_MODE: Voice CODEC Digital Interface Control

addr: 500004 hex R/W 16 bits

Bits 15..6 – Reserved

• Bit 5 – ENA: Enables Serial Transmission

1= Enabled

0= Not enabled

• Bit 4 – OSF: Output Sample Format

1 = 16 bits

0 = 8 bits