2-46
Functional Description
indicating an interrupt. This method is the fastest, but it diverts CPU time
from other system tasks. The preferred method of detecting interrupts in
most systems is hardware interrupts. In this case, the LSI53C1000
asserts the interrupt request (INTA/) line that interrupts the
microprocessor, causing the microprocessor to execute an interrupt
service routine. A hybrid approach uses hardware interrupts for long
waits and polling for short waits.
The SCSI interrupt is routed to PCI Interrupt INTA/.
2.2.16.2 Registers
The registers in the LSI53C1000 used for detecting or defining interrupts
are
Interrupt Status Zero (ISTAT0)
Interrupt Status One (ISTAT1), SCSI
SCSI Interrupt Status One (SIST1)
,
Status (DSTAT), SCSI Interrupt Enable Zero (SIEN0)
, and
. See the register
descriptions in
for additional information.
ISTAT – The ISTAT register includes the
Interrupt Status Zero (ISTAT0),
, and
registers. It is the only register that can be accessed as a slave
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/ 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 in order to clear it. This interrupt must be
cleared before servicing any other interrupts indicated by SIP or DIP. Do
not attempt to read the other chip status registers if the INTF bit is set,
but SIP or DIP are not set.
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.
Summary of Contents for LSI53C1000
Page 6: ...vi Preface...
Page 16: ...xvi Contents...
Page 28: ...1 12 Introduction...
Page 234: ...4 124 Registers...
Page 314: ...6 40 Specifications This page intentionally left blank...
Page 318: ...6 44 Specifications This page intentionally left blank...
Page 344: ...6 70 Specifications This page intentionally left blank...
Page 350: ...6 76 Specifications Figure 6 42 LSI53C1000 329 Ball Grid Array Bottom view...
Page 352: ...6 78 Specifications...
Page 360: ...A 8 Register Summary...
Page 376: ...IX 12 Index...