Register: 0x39

DMA Interrupt Enable (DIEN)

Read/Write

7

6

5

4

 

3

2

 

1

0

R

MDPE

BF

ABRT

 

SSI

SIR

 

R

IID

x

0

0

0

 

0

0

 

x

0

R

Reserved

 

 

 

 

 

 

7

MDPE

Master Data Parity Error

 

 

 

6

BF

Bus Fault

 

 

 

 

 

 

5

ABRT

Aborted

 

 

 

 

 

 

4

SSI

Single Step Interrupt

 

 

 

 

3

SIR

SCRIPTS Interrupt Instruction Received

 

2

R

Reserved

 

 

 

 

 

 

1

IID

Illegal Instruction Detected

 

 

 

0

This register contains the interrupt mask bits corresponding to the interrupting conditions described in the DMA Status (DSTAT) register. An interrupt is masked by clearing the appropriate mask bit. Masking an interrupt prevents IRQ/ from being asserted for the corresponding interrupt, but the status bit is still set in the DSTAT register. Masking an interrupt does not prevent setting the Interrupt Status Zero (ISTAT0) DIP. All DMA interrupts are considered fatal, therefore SCRIPTS stops running when this condition occurs, whether or not the interrupt is masked. Setting a mask bit enables the assertion of IRQ/ for the corresponding interrupt. (A masked nonfatal interrupt does not prevent unmasked or fatal interrupts from getting through; interrupt stacking begins when either the Interrupt Status Zero (ISTAT0) SIP or DIP bit is set.)

The IRQ/ output is latched. Once asserted, it will remain asserted until the interrupt is cleared by reading the appropriate status register. Masking an interrupt after the IRQ/ output is asserted does not cause deassertion of IRQ/.

SCSI Registers

4-69

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Image 161
LSI 53C875A DMA Interrupt Enable Dien Read/Write, Master Data Parity Error Bus Fault, Illegal Instruction Detected