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5-20 SCSI SCRIPTS Instruction Set
Table Relative
Treats the alternate jump address as a relative jump and
fetches the device ID, synchronous offset, and
synchronous period indirectly. The value in bits [23:0] of
the first four bytes of the SCRIPTS instruction is added
to the data structure base address to form the fetch
address.
Sel Select with ATN/ 24
This bit specifies whether SATN/ is asserted during the
selection phase when the LSI53C875A is executing a
Select instruction. When operating in Initiator mode, set
this bit for the Select instruction. If this bit is set on any
other I/O instruction, an illegal instruction interrupt is
generated.
R Reserved [23:20]
ENDID[3:0] Encoded SCSI Destination ID [19:16]
This 4-bit field specifies the destination SCSI ID for an I/O
instruction.
R Reserved [15:11]
CC Set/Clear Carry 10
This bit is used in conjunction with a Set or Clear
instruction to set or clear the Carry bit. Setting this bit
withaSetinstructionassertstheCarrybitintheALU.
Clearing this bit with a Clear instruction deasserts the
Carry bit in the ALU.
TM Set/Clear Target Mode 9
This bit is used in conjunction with a Set or Clear
instruction to set or clear Target mode. Setting this bit
with a Set instruction configures the LSI53C875A as a
Target device (this sets bit 0 of the SCSI Control Zero
(SCNTL0) register). Clearing this bit with a Clear
instruction configures the LSI53C875A as an Initiator
device (this clears bit 0 of the SCNTL0 register).
Command Table Offset
Absolute Jump Offset