Interrupt Service Thread Latency

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Interrupt Service Thread Latency

Wed Oct 13, 2010 2:21 pm

I'm testing the Interrupt Service Thread (IST) Latency times
on a AT91SAM9263 with Windows CE 6.0 and free Atmel BSP.

I'm using GPIO output to test the delay between the ISR and IST:
most of the times the delay is less than 100us but sometimes
I can see latency times up to 20ms!
So that if I have interrupt frequency higher than 50Hz
the interrupt event is lost.

Note: I'm usign maximum priority for IST (priority = 0).
It seemes strange but this problems happens only in the
Release build of the AT91SAM9263EK_DEMO project.

The ISR works correctly but the interrupt event to the IST is delayed.

Do you have any idea of which is the problem?
Is it possible that a thread is blocking this high priority interrupt event?

Thank you for your answer.

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