Embedded Systems Design, 2nd Edition

Interrupts and exceptions 205

Interrupt controllers

In many embedded systems there are more external sources

for interrupts than interrupt pins on the processor. In this case, it

is necessary to use an interrupt controller to provide a larger

number of interrupt signals. An interrupt controller performs

several functions:

• It provides a large number of interrupt pins that can be

allocated to many external devices. Typically this is at least

eight and higher numbers can be supported by cascading

two or more controllers together. This is done on the IBM

PC AT where two 8 port controllers are cascaded to give 15

interrupt levels. One level is lost to provide ...