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Operating Registers
5-20
SYM53C810A Data Manual
Registers 10-13 (90-93)
Data Structure Address (DSA)
Read/Write
T his 32-bit register contains the base address used
for all table indirect calculations. T he DSA register
is usually loaded prior to starting an I/O, but it is
possible for a SCRIPT S Memory Move to load the
DSA during the I/O.
During any Memory-to-Memory Move operation,
the contents of this register are preserved. T he
power-up value of this register is indeterminate.
Register 14 (94)
Interrupt Status (ISTAT )
(Read/Write)
T his is the only register that can be accessed by the
host CPU while the SYM53C810A is executing
SCRIPT S (without interfering in the operation of
the SYM53C810A). It may be used to poll for in-
terrupts if hardware interrupts are disabled. T here
may be stacked interrupts pending; read this regis-
ter after servicing an interrupt to check for stacked
interrupts. For more information on interrupt han-
dling refer to Chapter 2, “Functional Description.”
Bit 7
ABRT (Abort operation)
Setting this bit aborts the current operation
being executed by the SYM53C810A. If this
bit is set and an interrupt is received, reset this
bit before reading the DSTAT register to pre-
vent further aborted interrupts from being gen-
erated. T he sequence to abort any operation is:
1. Set this bit.
2. Wait for an interrupt.
3. Read the ISTAT register.
4. If the SCSI Interrupt Pending bit is set,
then read the SIST 0 or SIST 1 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 00h value to this register.
6. Read the DSTAT register to verify the
aborted interrupt and to see if any other
interrupting conditions have occurred.
Bit 6
SRST (Software reset)
Setting this bit resets the SYM53C810A. All
operating registers are cleared to their default
values and all SCSI signals are deasserted. Set-
ABRT
7
SRST
6
SIGP
5
SEM
4
CON
3
INTF
2
SIP
1
DIP
0
Default>>>
0
0
0
0
0
0
0
0