Read/Write Packet | 7 |
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NOTE 1. Refer to Chapter 3.
S:
2.Refer to the following scatter/gather table format.
3.The interrupt level of this firmware can be from level 0 to 7. It should be kept the same throughout the firmware execution; i.e., when the user has chosen a specific interrupt level, it must not be changed until there is no outstanding command.
4.The return vector should point to the user return routine at all times for the proper return path.
5.Because both the interrupt vector and the return vector use the Vector Base Register (VBR) to locate the proper address to resume the operation, the VBR should not be changed if there are any outstanding SCSI commands.
6.During scatter/gather operation, no automatic RETRY is performed by SCSI firmware and the scatter/gather table contents could be modified by the firmware when the command is completed.
DMA Scatter/Gather Table Entry
Each scatter/gather table entry has two longwords: first one is DMA memory address, second is control/byte count.
310
DMA MEMORY ADDRESS (32-BIT)
X
0
0
0
0
1
0
1
XXXXXXXX XXXX XXXX XXXX XXXX
function code (3 bits)
1 = link to next entryFor example $5 is
0 = no link, last entryused here (supervisory data space)
