
SCSI Registers
4-41
interrupts). The DIP bit in the
Interrupt Status Zero (ISTAT0)
register is
also cleared. It is possible to mask DMA interrupt conditions individually
through the
DMA Interrupt Enable (DIEN)
register.
When performing consecutive 8-bit reads of the
DMA Status (DSTAT)
,
SCSI Interrupt Status Zero (SIST0)
and
SCSI Interrupt Status One
(SIST1)
registers (in any order), insert a delay equivalent to 12 CLK
periods between the reads to ensure that the interrupts clear properly.
See
Chapter 2, “Functional Description”
for more information on
interrupts.
DFE
DMA FIFO Empty
This status bit is set when the DMA FIFO is empty. It is
possible to use it to determine if any data resides in the
FIFO when an error occurs and an interrupt is generated.
This bit is a pure status bit and does not cause an
interrupt.
7
MDPE
Master Data Parity Error
This bit is set when the SYM53C1010 SCSI function,
acting as a PCI master, detects a data parity error, or,
acting as a target device, signals a parity error during a
data phase. This bit is completely disabled by the Master
Parity Error Enable bit (bit 3 of
Chip Test Four (CTEST4)
).
6
BF
Bus Fault
This bit is set when a PCI bus fault condition is detected.
A PCI bus fault can only occur when the SYM53C1010
SCSI function is bus master, and is defined as a cycle
that ends with a Bad Address or Target Abort Condition.
5
ABRT
Aborted
This bit is set when an abort condition occurs. An abort
condition occurs when a software abort command is
issued by setting bit 7 of the
Interrupt Status Zero
(ISTAT0)
register.
4
SSI
Single Step Interrupt
If the Single-Step Mode bit in the
DMA Control (DCNTL)
register is set, this bit is set and an interrupt generated
after successful execution of each SCRIPTS instruction.
3
SIR
SCRIPTS Interrupt Instruction Received
This status bit is set whenever an interrupt instruction is
evaluated as true.
2