LSI 53C810A - Manual (Page 125)

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Register: 0x42 (0xC2)
SCSI Interrupt Status Zero (SIST0)
Read Only
Reading the SCSI Interrupt Status Zero (SIST0) register returns the
status of the various interrupt conditions, whether they are enabled in the
SCSI Interrupt Enable Zero (SIEN0) register or not. Each bit set indicates
an occurrence of the corresponding condition. Reading the SCSI
Interrupt Status Zero (SIST0) clears the interrupt status.
Reading this register clears any bits that are set at the time the register
is read, but does not necessarily clear the register because additional
interrupts may be pending (the LSI53C810A stacks interrupts). SCSI
interrupt conditions may be individually masked through the
SCSI
Interrupt Enable Zero (SIEN0) 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 the interrupts clear properly. Also,
if reading the registers when both the
Interrupt Status (ISTAT) SIP and
DIP bits may not be set, read the SCSI Interrupt Status Zero (SIST0) and
SCSI Interrupt Status One (SIST1) registers the DMA Status (DSTAT)
register to avoid missing a SCSI interrupt. For more information on
interrupts, refer to
Chapter 2, “Functional Description.”
M/A Initiator Mode: Phase Mismatch;
Target Mode: SATN/ Active
7
In the initiator mode, this bit is set if the SCSI phase
asserted by the target does not match the instruction.
The phase is sampled when SREQ/ is asserted by the
target. In target mode, this bit is set when the SATN/
signal is asserted by the initiator.
CMP Function Complete 6
This bit is set when an arbitration only or full arbitration
sequence is completed.
7 6 5 4 3 2 1 0
M/A CMP SEL RSL SGE UDC RST PAR
0 0 0 0 0 0 0 0