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Timing an ISR on ADSP-21479

Question asked by pozzi on Jun 26, 2012
Latest reply on Jun 28, 2012 by pozzi

I am using an ADSP-21479.  I have multiple interrupts in use.  Interrupts are NOT nested.

 

I am toggling a pin inside one of the ISRs to time how long it takes to execute.  I put the pin high as the first instruction in the ISR and then I put the pin low as the last instruction in the ISR.

 

I look at the state of the pin using an oscilloscope and I see that the pin can be high any where from 0.2 usec to as much as 7 usec.  What can cause such a large timing difference?  If interrupts are not nested what could possibly be causing the time spent in the ISR to be so drastically different each time it executes?

 

Thank you,

Pam

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