Embedded Systems Design, 2nd Edition

Interrupts and exceptions 195

processors insist on the maintain until serviced approach with

interrupts. Any subsequent interrupts that have the same level

will be maintained after the first one has been serviced and its

signal removed. When the exception processing is completed, the

remaining interrupts will be recognised and processed one by one

until they are all serviced.

The interrupt mechanism

Once an interrupt or exception has been recognised, then

the processor goes through an internal sequence to switch the

processing thread and activate the ISR or exception handler that

will service the interrupt or exception. The actual process and,

more importantly, ...