2-44
Functional Description
during the SCRIPTS operation. Therefore, it is the register that is polled
when polled interrupts are used. It is also the first register that should be
read after the INTA/ (or INTB/) pin is asserted in association with a
hardware interrupt. The INTF (Interrupt-on-the-Fly) bit should be the first
interrupt serviced. It must be written to one to be cleared. This interrupt
must be cleared before servicing any other interrupts.
See Register 0x14,
Interrupt Status Zero (ISTAT0)
, Bit 5 signal process
in
for additional information.
The host (C Code) or the SCRIPTS code could potentially try to access
the mailbox bits at the same time.
If the SIP bit in the
Interrupt Status Zero (ISTAT0)
register is set, then a
SCSI-type interrupt has occurred and the
and
SCSI Interrupt Status One (SIST1)
registers should be read.
If the DIP bit in the
Interrupt Status Zero (ISTAT0)
register is set, then a
DMA-type interrupt has occurred and the
register
should be read.
SCSI-type and DMA-type interrupts may occur simultaneously, so in
some cases both SIP and DIP may be set.
SIST0 and SIST1 – The
SCSI Interrupt Status Zero (SIST0)
and
registers contain SCSI-type interrupt bits.
Reading these registers determines which condition or conditions caused
the SCSI-type interrupt, and clears that SCSI interrupt condition.
If the LSI53C896 is receiving data from the SCSI bus and a fatal interrupt
condition occurs, the chip attempts to send the contents of the DMA
FIFO to memory before generating the interrupt.
If the LSI53C896 is sending data to the SCSI bus and a fatal SCSI
interrupt condition occurs, data could be left in the DMA FIFO. Because
of this the DMA FIFO Empty (DFE) bit in
should be
checked.
If this bit is cleared, set the CLF (Clear DMA FIFO) and CSF (Clear SCSI
FIFO) bits before continuing. The CLF bit is bit 2 in
. The CSF bit is bit 1 in
*
Summary of Contents for LSI53C896
Page 6: ...vi Preface...
Page 16: ...xvi Contents...
Page 88: ...2 62 Functional Description...
Page 112: ...3 24 Signal Descriptions...
Page 306: ...6 38 Specifications This page intentionally left blank...
Page 310: ...6 42 Specifications This page intentionally left blank...
Page 338: ...6 70 Specifications Figure 6 40 LSI53C896 329 BGA Bottom View...
Page 340: ...6 72 Specifications...
Page 346: ...A 6 Register Summary...
Page 362: ...IX 12 Index...