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FUSION878A

PCI Video Decoder

Conexant Systems 

Fusion 878A

PCI Video Decoder

1.0 Product Overview

1.2 Detailed Features

1.2.5 Video DMA Channels

The Fusion 878A enables separate destinations for the odd and even fields, each

controlled by a pixel RISC instruction list. This instruction list is created by the

Fusion 878A device driver and placed in the host memory. The instructions

control the transfer of pixels to target memory locations on a byte resolution

basis. Complex clipping can be accomplished by the instruction list, blocking the

generation of PCI bus cycles for pixels that are not to be seen on the display.

The DMA channels can be programmed on a field basis to deliver the video

data in packed or planar format. In packed mode, YCrCb data is stored in a single

continuous block of memory. In planar mode, the YCrCb data is separated into

three streams which are burst to different target memory blocks. Having the video

data in planar format is useful for applications where the data compression is

accomplished via software and the CPU.

1.2.6 Audio DMA Channels

The audio channel delivers 8-bit or 16-bit digital samples of a digital

frequency-multiplexed analog signal to system memory in packets of DWORDs.

A RISC program controls the audio DMA Program Initiator. The flow of audio

data and audio RISC instructions is completely independent and asynchronous to

the flow of video data and video RISC instructions.

Since the audio data path operates in continuous transfer mode (no sync gaps),

both the analog and the digital audio inputs can be used for other data capture

applications. The analog input offers 360 kHz usable BW at 8 effective bits or 100

kHz usable BW at 12 effective bits. The digital input offers up to 20 Mbps for the

parallel mode and 40 Mbps for the serial mode.

The audio DMA channel controller is similar to the video DMA controller in

that it supports packed mode RISC instructions. It also only interfaces to one

35 x 36 FIFO and its associated 6-bit DWORD counter.

The audio PCI initiator is identical to the video PCI initiator; they have the

same DMA controller interface and the same support for interrupts and

configuration space. Since the video and audio initiators are independent, each

can handle retries without inhibiting the other. Thus, the audio function can

initiate transfers to the host bridge even when a GFX target is retrying the video

function.

The audio PCI target is similar to the video PCI target with respect to

interrupts, configuration space, memory-mapped registers, and parity error

checking. The main difference in audio is that all of the memory-mapped

registers remain within the PCI clock and 32-bit interface domain. There is no

register interface to the audio clock domain. Thus, this target never issues a

disconnect or a retry.

1.2.7 Data Transport Engine

The Fusion 878A data transport engine operates in instruction mode. Video data

and audio data are delivered over the PCI bus under independent control.

100600B

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