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Interrupt latency, dead time, ADSP21489

Question asked by MarcZ on Apr 22, 2013
Latest reply on May 28, 2013 by JamesH



I am working on the ADSP21489 EZ-Kit.

I have done some simple experiments with the interrupt. I made a tight loop in the main, where I toggle a IO pin. I also toggle 10 times another pin in the interrupt.

We used the scope to evaluate, not only the interrupt latency, but what the processor can do in between the time that the interrupt happens, and the time we actually get there. In other words, this experiment allow us to evaluate the "dead time" caused by an interrupt.


Here is some screenshots from the scope:

experiment interrupt.jpg

                    Time between the interrupt happening and the pin toggle. (~500ns!! So 500ns where the processor is "dead" ?!)


experiment interrupt dt.jpg

                    Time between the end of toggle and the go back to the main loop (~400ns)


I tried to do kind of the same experiment with calling a function instead of enable an interrupt in order to see how fast it is to toggle another IO pin with a function calling. And obviously to see if this is really the interrupt which causes that.


experiment fuction.jpg

                    Pink = function called, yellow = toggle IO in main loop  (~80ns)


If you have any comments or suggestion, I would be glad to read it.


Thank you,