LSI LSI53C895A Technical Manual page 236

5-14
Target Mode
OPC2 OPC1 OPC0
0
0
0
0
1
Reselect Instruction
The LSI53C895A 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 LSI53C895A wins arbitration, it attempts to reselect
the SCSI device whose ID is defined in the destination ID
field of the instruction. Once the LSI53C895A 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 LSI53C895A 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
the LSI53C895A to Initiator mode if it is reselected, or to
Target mode if it is selected.
Disconnect Instruction
The LSI53C895A disconnects from the SCSI bus by
deasserting all SCSI signal outputs.
Wait Select Instruction
If the LSI53C895A is selected, it fetches the next
instruction from the address pointed to by the
SCRIPTS Pointer (DSP)
SCSI SCRIPTS Instruction Set
Instruction Defined
0 0 Reselect
0 1 Disconnect
1 0 Wait Select
1 1 Set
0 0 Clear
DMA SCRIPTS Pointer (DSP)
DMA Next Address (DNAD)
register.
SCSI Chip ID (SCID)
register. Manually set
register.
register.
DMA