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6-14 Instruction Set of the I/O Processor
Reselect Instruction
1. The LSI53C810A 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 LSI53C810A wins arbitration, it attempts to
reselect the SCSI device whose ID is defined in the
destination ID field of the instruction. Once the
LSI53C810A 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 LSI53C810A 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 LSI53C810A to Initiator mode if it is
reselected, or to Target mode if it is selected.
Disconnect Instruction
The LSI53C810A disconnects from the SCSI bus by
deasserting all SCSI signal outputs.