ZR36067 データシートの表示（PDF） - Unspecified

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ZR36067

AV PCI CONTROLLER

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AV PCI CONTROLLER

mand” information, written by the host, for the next available

buffer. Table 10 shows the interpretation for this

case.

Table 10: STAT_COM entry content, when

STAT_BIT=0

Bit

31:2

1

0

Content

FRAG_TAB_PTR[31:2]

FRAG_TAB_PTR [1]

STAT_BIT

Description

The address pointer to the

fragment table of the next buffer

to be used. The 2 l.s. bits of the

address must be ‘0’ - that is, the

address must be doubleword

aligned.

Must to be ‘0‘.

Must be ‘0’ to indicate that the

table entry is a command.

If the STAT_BIT=‘1‘, the content of the entry is the “status” infor-

mation, written by the ZR36067, of the most recently processed

field or frame. Table 11 shows the interpretation for this case.

Table 11: STAT_COM entry content, when

STAT_BIT=1

Bit

Content

31:24 F_CNT[7:0]

23

22:1 F_LENGTH[21:0]

0 STAT_BIT

Description

The serial number, modulo 256, of the

most recent field or frame. Used in

compression only.

Reserved, set to ‘0’.

The length of the most recently com-

pressed field or frame in bytes, used in

compression only. The length is dou-

bleword aligned, so bits 2..1 are

always ‘0‘.

‘1‘, indicating that this table entry is a

status written by the ZR36067.

9.2 Fragment Table

The Fragment Table (Figure 9) defines the structure of the allo-

cated memory for each code buffer. The table has N entries for

N allocated fragments. Each entry holds two doublewords:

• first doubleword - the physical address of the fragment (must

be doubleword aligned).

• second doubleword - has the following fields:

- bits 20:1, the fragment length in doublewords (the frag-

ment must be doubleword aligned),

- bit 0, F (“Final” bit), when ‘1’ indicates that this fragment is

the final fragment of the buffer,

- bits 31:21, unused, must be 0.

9.3 JPEG Compression Modes

The sequence of actions performed by the host software and the

ZR36067 is as follows:

• The host allocates the first four code buffers and writes out

the code buffer table and the fragment table.

• The host loads the ZR36067’s I_STAT_COM_PTR register

with the base address of the code buffer table.

• After the start of the compression process, the ZR36067

starts filling the fragments of the first code buffer with the

compressed data of the first field or frame.

• After successfully completing transfer of the compressed

data of a field or frame, the ZR36067 writes the status infor-

mation back to the STAT_COM entry of the current buffer. It

sets the STATUS_BIT in the STAT_COM entry, declaring its

content as status. It then issues an interrupt, and starts the

next field or frame process.

• 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 ZR36067 polls the STAT_COM entry

until the buffer is available.

• 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 checks F_CNT to determine

whether any fields/frames were dropped. It records the code

buffer information, updates the fragment table and

STAT_COM entry of the code buffer, and returns it by reset-

ting STAT_BIT to ‘0’.

Several scenarios might cause a field or frame process to be

unsuccessful:

• The allocated code buffer memory was smaller than the ac-

tual field/frame code volume (the ZR36067 fills the final

fragment, but the field/frame code transfer is not complete).

• A ZR36060 strip memory overflow occurs during the field/

frame compression (might be caused by very large PCI bus

latency).

• The compression of a field has not ended by the time the

trailing edge of the next VSync is detected.

After an unsuccessful field/frame process in compression, the

ZR36067 does not issue an interrupt, re-uses the current code

buffer - that is, does not over-write its STAT_COM entry, and

restarts with the next field or frame. The software can determine

the number of fields or frames that were skipped by reading

F_CNT.

9.4 JPEG Decompression Modes

The sequence of actions performed by the host software and the

ZR36067 is as follows:

• The host allocates the first four code buffers and writes out

the code buffer table and the fragment table.

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