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If the scatter/gather field at byte offset $10 in the user packet is not zero, the
address at offset $4 is taken as a scatter/gather table address. Otherwise the
address is the READ/WRITE buffer starting address.
A typical scatter/gather table example would be:
Scatter/Gather Table Example
The READ and WRITE commands build a ten byte command descriptor block
based on the previous ATTACH and the READ/WRITE command.
READ/WRITE Command CDB
ENTRY NUMBER
ENTRY COMMENTS
1 0018E400 DMA memory address
85001200 Link flag, function code = 5,
byte count
2 0022C800 DMA memory address
85000800 Link flag, function code = 5,
byte count
3 00203000 DMA memory address
05001200 Link flag = 0 (last entry),
function code
= 5, byte count
BYTE OFFSET
VALUE COMMENTS
0 28 (read), 2A (write) Command code
1 00 LUN is inserted into bits 7-5
2 (Note 1) Logical block address
3 (Note 1) Logical block address
4 (Note 1) Logical block address
5 (Note 1) Logical block address
600Reserved
7 (Note 2) Transfer length
8 (Note 2) Transfer length
9 00 Control byte: no link, no flag