Avago Technologies LSI53C895A - Manual (Page 243)

I/O Instruction 5-21
Since SACK/ and SATN/ are Initiator signals, they are not
asserted on the SCSI bus unless the LSI53C895A is
operating as an Initiator or the SCSI Loopback Enable bit
is set in the
SCSI Test Two (STEST2) register.
The Set/Clear SCSI ACK/, ATN/ instruction is 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.
R Reserved [2:0]
5.4.2 Second Dword
SA Start Address [31:0]
This 32-bit field contains the memory address to fetch the
next instruction if the selection or reselection fails.
If relative or table relative addressing is used, this value
is a 24-bit signed offset relative to the current
DMA
SCRIPTS Pointer (DSP) register value.
31 24 23 16 15 8 7 0
DMA SCRIPTS Pointer Save (DSPS) Register
x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x