Avago Technologies LSI53C1000R - Manual (Page 263)

I/O Instructions 5-21
Version 2.2 Copyright © 2000–2003 by LSI Logic Corporation. All rights reserved.
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]
CA 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
with a Set instruction asserts the Carry bit in the ALU.
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 the target mode. Setting this bit with a Set
instruction configures the LSI53C1000R as a target device
(this sets bit 0 of the
SCSI Control Zero (SCNTL0) register).
Clearing this bit with a Clear instruction configures the
LSI53C1000R as an initiator device (this clears bit 0 of the
SCNTL0 register).
R Reserved [8:7]
A Set/Clear SACK/ 6
This bit is used in conjunction with a Set or Clear
instruction to assert or deassert SACK/.
The Set instruction asserts SACK/ on the SCSI bus. The
Clear instruction deasserts SACK/ on the SCSI bus. The
corresponding bit in the
SCSI Output Control Latch (SOCL)
register is set or cleared depending on the instruction
used. Because SACK/ is an initiator signal, it is not
asserted on the SCSI bus unless the LSI53C1000R is
operating as an initiator.
The Set/Clear SCSI ACK/, ATN/ instructions are used after
message phase Block Move operations to give the initiator
the opportunity to assert attention before acknowledging
the last message byte. For example, if the initiator wishes
to reject a message, it issues an Assert SCSI ATN
instruction before a Clear SCSI ACK instruction.