Test Your EQ (Engineering Quotient)

EQ #43

Some processors don’t have explicit control over the global interrupt mask; reenabling it is implicit in the execution of a “return from interrupt” instruction. Is there a workaround?

Yes, on most such processors, you can execute a subroutine call to a “return from interrupt” instruction while still in the master ISR, which will then return to the master ISR, but with interrupts enabled.

Check to see whether the “return from interrupt” affects any other processor state, such as popping a status word from the stack, and prepare the stack accordingly.

Also, beware that another interrupt could occur immediately thereafter, and make sure the master ISR is reentrant beyond that point.

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EQ #43

by Circuit Cellar Staff time to read: <1 min