Specifications

Interrupt Controller (V40)

OVERVIEW

This chapter describes the Interrupt Control Unit (ICU) and provides

The ICU is a programmable interface between interrupt-generating

peripherals and the CPU. The ICU monitors eight interrupt inputs

with programmable priority. When peripherals request service, the

ICU interrupts the CPU with a pointer to a service routine for the

highest priority device. This type of interrupt management is needed

for an efficient interface between the CPU and supporting peripheral

devices, such as serial controllers and counter/timers. The major

features of the ICU are as follows:

• Eight individually maskable interrupts

• Level- or edge-triggered interrupts

• Fixed and rotating prioritization

• Status available for polled operation

• Functionally equivalent to the 8259

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