LSI 53C875A - Manual (Page 215)

I/O Instruction 5-15
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 LSI53C875A 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 LSI53C875A to Initiator mode if it is reselected, or to
Target mode if it is selected.
Disconnect Instruction
The LSI53C875A disconnects from the SCSI bus by
deasserting all SCSI signal outputs.
Wait Select Instruction
If the LSI53C875A is selected, it fetches the next
instruction from the address pointed to by the
DMA
SCRIPTS Pointer (DSP) register.
If reselected, the LSI53C875A 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 LSI53C875A to Initiator mode when it is
reselected.
If the CPU sets the SIGP bit in the Interrupt Status Zero
(ISTAT0) register, the LSI53C875A aborts the Wait Select
instruction and fetches the next instruction from the
address pointed to by the 32-bit jump address field stored
in the
DMA Next Address (DNAD) register.
Set Instruction
When the SACK/ or SATN/ bits are set, the
corresponding bits in the
SCSI Output Control Latch
(SOCL) register are set. Do not set SACK/ or SATN/
except for testing purposes. When the target bit is set,
the corresponding bit in the
SCSI Control Zero (SCNTL0)
register is also set. When the carry bit is set, the
corresponding bit in the Arithmetic Logic Unit (ALU) is
set.
Note: None of the signals are set on the SCSI bus in Target
mode.
Clear Instruction