Embedded Systems Design, 2nd Edition

196 Embedded systems design

MC6800, the context information that the processor needs to

preserve is saved on the external stack.

When the interrupt occurs, the processor context informa-

tion such as the return address, copies of the internal status

registers and so on are stored out on the stack in a stack frame.

These stack frames can vary in size and content depending on the

source of the interrupt or exception.

2 clocks 2–200 clocks 12–200 clocks 3 clocks

RECOGNISE

INTERRUPT

WAIT FOR CURRENT

INSTRUCTION TO

COMPLETE

STORE INTERNAL

INFORMATION ON

EXTERNAL STACK

GET

INTERRUPT

VECTOR

A typical processor interrupt sequence

When the interrupt processing is completed, ...