
SCSI Registers
5-47
4. If the SCSI Interrupt Pending bit is set, then read the
SCSI Interrupt Status Zero (SIST0) or SCSI Interrupt
Status One (SIST1) register to determine the cause of
the SCSI Interrupt and go back to Step 2.
5. If the SCSI Interrupt Pending bit is clear, and the DMA
Interrupt Pending bit is set, then write 0x00 value to
this register.
6. Read the DMA Status (DSTAT) register to verify the
aborted interrupt and to see if any other interrupting
conditions have occurred.
SRST
Software Reset
6
Setting this bit resets the SYM53C895. All operating
registers are cleared to their respective default values
and all SCSI signals are deasserted. Setting this bit does
not cause the SCSI RST/ signal to be asserted. This
reset does not clear the 53C700 ID Mode bit or any of
the PCI conguration registers. This bit is not self-
clearing; it must be cleared to clear the reset condition (a
hardware reset will also clear this bit).
SIGP
Signal Process
5
SIGP is a R/W bit that is writable at any time, and polled
and reset using Chip Test Two (CTEST2). The SIGP bit
can be used in various ways to pass a ag to or from a
running SCRIPTS instruction.
The only SCRIPTS instruction directly affected by the
SIGP bit is Wait For Selection/Reselection. Setting this bit
causes that instruction to jump to the alternate address
immediately. The instructions at the alternate jump
address should check the status of SIGP to determine
the cause of the jump. The SIGP bit may be used at any
time and is not restricted to the wait for
selection/reselection condition.
SEM
Semaphore
4
This bit can be set by the SCRIPTS processor using a
SCRIPTS register write instruction. The bit may also be
set by an external processor while the SYM53C895 is
executing a SCRIPTS operation. This bit enables the
SYM53C895 to notify an external processor of a
predened condition while SCRIPTS are running. The