Fusion 878A
1.0 Product Overview
PCI Video Decoder
1.2 Detailed Features
100600B
Conexant
1-5
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.