in the Interrupt Status (ISTAT) 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

7

 

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.

 

MDPE

Master Data Parity Error

6

 

This bit is set when the LSI53C810A as a master detects

 

a data parity error, or 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)).

 

BF

Bus Fault

5

 

This bit is set when a PCI bus fault condition is detected.

 

A PCI bus fault can only occur when the LSI53C810A is

 

bus master, and is defined as a cycle that ends with a

 

 

Bad Address or Target Abort Condition.

 

ABRT

Aborted

4

 

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 (ISTAT)

 

 

register.

 

SSI

Single Step Interrupt

3

 

If the Single Step Mode bit in the DMA Control (DCNTL)

 

register is set, this bit is set and an interrupt is generated

 

after successful execution of each SCRIPTS instruction.

SIRSCRIPTS Interrupt Instruction Received2

This status bit is set whenever an Interrupt instruction is evaluated as true.

5-21

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LSI 53C810A technical manual Dfe, Mdpe, Abrt, Ssi