Avago Technologies LSI53C825AE - Manual (Page 199)

I/O Instruction 5-15
Target Mode
Reselect Instruction
1. The LSI53C825A arbitrates for the SCSI bus by
asserting the SCSI ID stored in the SCSI Chip ID
(SCID) register. If it loses arbitration, it tries again
during the next available arbitration cycle without
reporting any lost arbitration status.
2. If the LSI53C825A wins arbitration, it attempts to
reselect the SCSI device whose ID is defined in the
destination ID field of the instruction. Once the
LSI53C825A wins arbitration, it fetches the next
instruction from the address pointed to by the
DMA
SCRIPTS Pointer (DSP) register. 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.
3. If the LSI53C825A 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) register.
Manually set the LSI53C825A to Initiator mode if it is
reselected, or to Target mode if it is selected.
Disconnect Instruction
The LSI53C825A disconnects from the SCSI bus by
deasserting all SCSI signal outputs.
OPC2 OPC1 OPC0 Instruction Defined
0 0 0 Reselect
0 0 1 Disconnect
0 1 0 Wait Select
0 1 1 Set
1 0 0 Clear