ZR36060PQC datasheet(22/46 Pages) ETC

22 / 46 page

Integrated JPEG CODEC

5.2.4 Transition between fields in decompression

For decompression, Figure 26 shows code transfer with 8-bit

interface and Figure 27 with 16-bit interface, at the transition

between consecutive fields showing the behavior of the EOI,

END and CBUSY signals.

JPEG compressed files input to the ZR36060 can be any size,

not required to be 32-bit, (double-word) aligned. The ZR36060

detects the EOI marker (0xFFD9), asserting EOI and CBUSY at

the next write strobe. Note that the host is allowed to write one

additional byte after the EOI marker code in 8-bit mode, or one

additional word after the word containing the second byte of the

EOI marker code 16-bit interface mode. This byte or word is dis-

carded by the ZR36060. If this discarded code byte or word

contained one or both bytes of the SOI marker of the next field,

the ZR36060 automatically reconstructs the marker when it

starts decompressing the next field.

Note that EOI and CBUSY may remain unasserted until END is

asserted, if the host has other means to detect the EOI marker

code and therefore does not issue the additional write strobe.

Attempts to access the code FIFO while CBUSY is asserted will

be held off until the FIFO is available again, using the ACK

signal. In this example, a WR pulse is shown being extended

until the next field begins, when CBUSY is deasserted.

END is asserted only after the whole decompressed field has

been output from the video interface. At this time the ZR36060

sets the EOAV status bit and returns to the IDLE state. Decom-

pression is started again when the ZR36060 senses the START

signal active.

Figure 26. 8-Bit Code Slave Mode Decompression, Transistion Between Consecutive Fields

ADDR[1:0]

ACK

CBUSY

EOI

DATA[7:0]

END

CODE for Field N

CODE for Field N+1

Start-Of-Image marker

End-Of-Image marker

End of Field

Process

Start new field process

due to START

Figure 27. 16-Bit Code Slave Mode Decompression, Transistion Between Consecutive Fields

ADDR[1:0]

ACK

CBUSY

EOI

DATA[7:0]

XXXX

XXFF

D9FF

FFFF

END

FFFF

FFD8

FFXX

CODE for Field N

CODE for Field N+1

Start-Of-Image marker

End-Of-Image marker

End of Field

Process

Start new field process

due to START

CODE[7:0]

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