2-48
Functional Description
DSTAT – The
register contains the status of
DMA-type interrupts whether they are enabled in DIEN or not. Reading
this register determines which condition(s) caused the DMA-type
interrupt, clears any interrupt related bits in DSTAT, and clears the DIP
bit in
Interrupt Status Zero (ISTAT0)
. Since the LSI53C1000 stacks
interrupts, reading DSTAT does not necessarily clear the register as
additional interrupts may be pending.
Bit 7 (DFE) in the
register, is purely a status bit; it
will not generate an interrupt and will not be cleared when read. DMA
interrupts do not flush the DMA or SCSI FIFOs before generating the
interrupt. Therefore, the DFE bit in the DSTAT register should be checked
after any DMA interrupt. If the DFE bit is cleared, the FIFOs must either
be cleared by setting the CLF (Clear DMA FIFO in CTEST3) and CSF
(Clear SCSI FIFO in STEST3) bits, or flushed by setting the FLF (Flush
DMA FIFO in CTEST3) bit.
SIEN0 and SIEN1 – The
SCSI Interrupt Enable Zero (SIEN0)
and
registers are the interrupt enable registers
for the SCSI interrupts in
SCSI Interrupt Status Zero (SIST0)
and
. Clearing the appropriate mask bit masks
an interrupt.
DIEN – The
register is the interrupt enable
register for DMA interrupts in
. Clearing the
appropriate mask bit masks an interrupt.
2.2.16.3 Fatal vs. Nonfatal Interrupts
A fatal interrupt, as the name implies, always causes the SCRIPTS to
stop running. All nonfatal interrupts become fatal when they are enabled
by setting the appropriate interrupt enable bit. Interrupt masking is
discussed in
All DMA interrupts are fatal.
The DMA interrupts are indicated by the DIP bit in
and one or more bits in
Some SCSI interrupts are nonfatal. The SCSI interrupts are indicated by
the SIP bit in the
Interrupt Status Zero (ISTAT0)
register and one or more
bits in
SCSI Interrupt Status Zero (SIST0)
register or
register.
Содержание LSI53C1000
Страница 6: ...vi Preface...
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Страница 28: ...1 12 Introduction...
Страница 234: ...4 124 Registers...
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Страница 350: ...6 76 Specifications Figure 6 42 LSI53C1000 329 Ball Grid Array Bottom view...
Страница 352: ...6 78 Specifications...
Страница 360: ...A 8 Register Summary...
Страница 376: ...IX 12 Index...