Rainbow Electronics AT76C551 - Manual (Page 47)

47
AT76C551
1612D–08/01
Voice CODEC
Register Set
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