SAA7785 Datasheet, PDF (17/68 Pages) NXP Semiconductors – ThunderBird Avenger PCI Audio Accelerator

Philips Semiconductors
ThunderBird Avenger^TM PCI Audio
Accelerator
FIGURE 5
S/PDIF TRANSMIT PORT BLOCK DIAGRAM
Audio Data
Holding
Registers
Audio Data
Shift
Registers
Validity Bit
Generation
Aux Data
Holding
Registers
Ctl/Channel
Stat Holding
Registers
User Data
Holding
Register
S/PDIF XMT
Port Status
Register
S/PDIF XMT
Control
Logic
CCLK
DCLK
S/PDIF XMT
Clock
Divider
Aux Data
Shift
Registers
Ctl/Channel
Stat Shift
Registers
User Data
Shift
Register
Preamble
Generation
Parity
Generation
MUX
Bi-Phase
Mark
Encoder
Preliminary Specification
SAA7785
Line
Driver
SPDO
VIRTUAL WRITE MASTER
Audio streams may be directed back to host memory from the DSP domain. The VWM has a data buffer capable of
storing enough audio data to burst into the host memory. The VWM is a simplified version of DMA and has more strin-
gent requirements on which and how many pages need to be allocated.
Using the VWM, the system programmer can redirect audio streams processed by the SAA7785 ThunderBird Aveng-
er^TM device and use them in any other audio device that resides in the system. The VWM is more efficient than the
DMA and should be the device of choice when redirecting audio streams back to the host. The device supports audio
sample rates from 8 to 48 KHz.
1999 Nov 12
17