ZR36057PQC Просмотр технического описания (PDF) - Zoran Corporation

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ZR36057PQC

ENHANCED PCI BUS MULTIMEDIA CONTROLLER

Zoran Corporation 

Enhanced PCI Bus Multimedia Controller

declaring that this buffer was already decompressed, issues

an interrupt, and starts the next field/frame process. It reads

the next STAT_COM entry from the code buffer table. If the

buffer is available, that is, the STAT_BIT=‘0‘ indicating it

contains the code of a new field/frame, the ZR36057 starts

transferring its fragments for decompression.

• If a new code buffer is unavailable at the beginning of a field

or frame process (that is, if the STATUS_BIT of the next

buffer entry is ‘1’), the ZR36057 repeats decompression of

the last available code buffer.

• When the host receives the interrupt, it checks the

STAT_COM entries in the code buffer table. For each entry

whose STAT_BIT=’1’, the host loads compressed data into

a new code buffer and updates its fragment table, then re-

turns the buffer by resetting its STAT_BIT to ‘0’.

Important Note:

In Motion Video Decompression mode, if the ZR36057 starts a

new fragment when the Code FIFO is exactly full, the Code FIFO

can sometimes overflow.

There are two possible ways to deal with this problem:

1. Copying the fragmented buffer into a single-fragment buffer

before playing it back.

Implementing this alternative may cause some performance

degradation due to the additional memory-to-memory copying.

2. Configuring the Code FIFO threshold to be low enough.

If the Code FIFO threshold is low enough, the Code FIFO will

never reach fullness. The maximum length of a single PCI burst

is limited, and after the Code FIFO gets above its threshold, the

PCI bus is not requested again.

The recommended parameters of the ZR36057 for this work-

around option are:

• The Triton bit (in the Video Display Configuration Register)

should be 0. This bit causes the ZR36057’s REQ signal to

be de-asserted immediately after the bus was granted. Typi-

cally (on machines with Triton PCI chip set), this causes the

GNT signal to be de-asserted. The ZR36057’s burst length

is then determined by the Latency Timer parameter.

• Master Latency Timer = 48 (in the PCI Configuration Space

Register.

• JPEGCodTrshold (in the JPEG Code FIFO Threshold Reg-

ister = 20.

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