Specifications

Interrupt Controller (V40)

IMDW

IMDW controls the method of reading status from the ICU and

enables a special type of interrupt masking.

The format of the IMDW is shown in Figure 8-9. The first two

bits are used to select the IRQ and IIS registers so they can be

read by the application software. A logical 1 in bit 0 selects the

IIS register and a logical 0 selects the IRQ register. A logical 1 in

the SR bit (bit 1) enables the reading of the IRQ and IIS registers.

IMDW

Address: Base + 0

Access: Write

76543210

IS/SR

00 No operation

01 No operation

10 Int. Request (IRQ) selected

11 Int. In Service (IIS) selected

POL

Polled Status

0 No operation

1 Polling command

SNM EXCN

Nesting Mode 2

01 No operation

10 Exceptional nesting mode

release

11 Exceptional nesting mode

set

—

Figure 8–9. Interrupt Mode Word.

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