LSI53C875 LSI Logic, LSI53C875 Datasheet - Page 209

• Manufacturer Part Number: LSI53C875
• Description: PCI to Ultra SCSI I/O Processor
• Manufacturer: LSI Logic

I/O Instruction
Target Mode
OPC2 OPC1 OPC0
0
0
0
0
1
Reselect Instruction
The LSI53C875 arbitrates for the SCSI bus by asserting
the SCSI ID stored in the
If it loses arbitration, it tries again during the next
available arbitration cycle without reporting any lost
arbitration status.
If the LSI53C875 wins arbitration, it attempts to reselect
the SCSI device whose ID is defined in the destination ID
field of the instruction. Once the LSI53C875 wins
arbitration, it fetches the next instruction from the address
pointed to by the
This way the SCRIPTS can move on to the next
instruction before the reselection completes. It continues
executing SCRIPTS until a SCRIPT that requires a
response from the Initiator is encountered.
If the LSI53C875 is selected or reselected before winning
arbitration, it fetches the next instruction from the address
pointed to by the 32-bit jump address field stored in the
DMA Next Address (DNAD)
LSI53C875 to Initiator mode if it is reselected, or to Tar-
get mode if it is selected.
Disconnect Instruction
The LSI53C875 disconnects from the SCSI bus by
deasserting all SCSI signal outputs.
Wait Select Instruction
If the LSI53C875 is selected, it fetches the next
instruction from the address pointed to by the
SCRIPTS Pointer (DSP)
0
0
1
1
0
0
1
0
1
0
DMA SCRIPTS Pointer (DSP)
Instruction Defined
Reselect
Disconnect
Wait Select
Set
Clear
register.
SCSI Chip ID (SCID)
register. Manually set the
DMA
register.
register.
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