Test Your EQ (Engineering Quotient)

EQ #42

What are some of the problems associated with software interrupt priorities?

For one thing, the startup latency of all the ISRs is increased by the time spent in the “master” ISR. This can be a problem in time-critical systems.

This scheme allows interrupts to be nested, so the stack must be large enough to handle the worst-case nesting of ISRs, on top of the worst-case nesting of non-interrupt subroutine calls. Finally, it is very tricky to do this in anything other than assembly language. If you want to use a high-level language, you’ll need to be intimately familiar with the language’s run-time library and how it handles interrupts and reentrancy in general.


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