ZR36060PQC datasheet(19/46 Pages) ETC

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Integrated JPEG CODEC

5.2 Slave Mode

In Slave mode, access to the internal code FIFO is accomplished

using the host interface, by reading or writing (depending on

compression or decompression mode respectively) to direct

access address zero (ADDR[1:0]=00b). The data bus width can

be 8 or 16 bits, depending on the Code16 parameter:

• 8-bit width (Code16 = 0). Only DATA[7:0] is used for the

code transfer.

• 16-bit width (Code16 = 1). CODE[7:0] is an extension of DA-

TA[7:0] to transfer 16-bit words. The byte ordering can be

exchanged using the Endian parameter.

Code Slave mode accesses are asynchronous (Figure 22). The

CS (Code Chip-Select) and ADDR[1:0] inputs can be deasserted

after every RD or WR cycle, or, in order to achieve the best per-

formance, left asserted for a burst of code transfer cycles.

The host must select one of three different methods to hand-

shake with the ZR36060 throughout the compression/

decompression process:

• use of the CBUSY signal, or

• use of the ACK signal, or

• by polling the CFIFO level bits.

CBUSY is used as an indication of the empty/full status of the

internal code FIFO of the ZR36060. When CBUSY is active

(low), it means that the code FIFO is empty (during compression)

or full (during decompression). When the host uses this signal, it

must sample CBUSY prior to each code access, and hold off the

assertion of RD or WR until CBUSY is deasserted.

The ZR36060’s ACK signal indicates permission to a complete

the current cycle. Assertion of ACK indicates that the internal

code FIFO is not empty (during compression) or not full (during

Figure 20. Master Mode Operation of the Code Bus,

with CFIS=0b (1 VCLKx2 Per Transfer)

VCLKx2

CCS

COE

Code Read (Decompression)

CBUSY

CODE[7:0]

(input)

CCS

CWE

Code Write (Compression)

CBUSY

CODE[7:0]

(output)

Figure 21. Master Mode Operation of the Code Bus,

with CFIS=1b (2 VCLKx2 Per Transfer)

VCLKx2

CCS

COE

Code Read (Decompression)

CBUSY

CODE[7:0]

(input)

CCS

CWE

Code Write (Compression)

CBUSY

CODE[7:0]

(output)

CS can be pulsed, or maintained active for burst of read or write pulses.

ACK is not granted when CBUSY is active, in both compression and

decompression.

The top example (compression) shows a system using CBUSY to decide when to

perform the next RD strobe.

The bottom example (decompression) shows a system using ACK grant to decide

when to terminate the current strobe. Note the extension of the WR cycle when

the FIFO is full.

Notes: 1.

Figure 22. Slave Mode Operation of the Code Bus

ADDR[1:0]

Code Read (Compression)

ACK

CBUSY

DATA[7:0]

(CODE[7:0])

CFIFO Empty

(Stall Access)

Cannot perform

a new strobe

ADDR[1:0]

Code Write (Decompression)

ACK

CBUSY

DATA[7:0]

(CODE[7:0])

CFIFO Empty

(Stall Access)

Strobe is held low

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