Register: 0x14

Interrupt Status Zero (ISTAT0)

Read/Write

7

6

5

4

3

2

1

0

ABRT

SRST

SIGP

SEM

CON

INTF

SIP

DIP

 

 

 

 

 

 

 

 

0

0

0

0

0

0

0

0

 

 

 

 

 

 

 

 

This register is accessible by the host CPU while a LSI53C875A is executing SCRIPTS (without interfering in the operation of the function). It is used to poll for interrupts if hardware interrupts are disabled. Read this register after servicing an interrupt to check for stacked interrupts.

ABRT

Abort Operation

7

 

Setting this bit aborts the current operation under

 

 

execution by the LSI53C875A. If this bit is set and an

 

 

interrupt is received, clear this bit before reading the DMA

 

Status (DSTAT) register to prevent further aborted

 

 

interrupts from being generated. The sequence to abort

 

any operation is:

 

 

1.

Set this bit.

 

 

2.

Wait for an interrupt.

 

 

3.

Read the Interrupt Status Zero (ISTAT0) and

 

 

 

Interrupt Status One (ISTAT1) registers.

 

 

4.

If the SCSI Interrupt Pending bit is set, then read the

 

 

SCSI Interrupt Status Zero (SIST0) or SCSI Interrupt

 

 

Status One (SIST1) register to determine the cause

 

 

of the SCSI Interrupt and go back to Step 2.

 

 

5.

If the SCSI Interrupt Pending bit is clear, and the

 

 

 

DMA Interrupt Pending bit is set, then write 0x00

 

 

 

value to this register.

 

 

6.

Read the DMA Status (DSTAT) register to verify the

 

 

aborted interrupt and to see if any other interrupting

 

 

conditions have occurred.

 

SRST Software Reset6

Setting this bit resets the LSI53C875A. All operating registers are cleared to their respective default values and all SCSI signals are deasserted. Setting this bit does not assert the SCSI RST/ signal. This reset does not

4-48Registers

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Image 140
LSI 53C875A technical manual Interrupt Status Zero ISTAT0 Read/Write, Abort Operation, Srst Software Reset6