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Edge Triggered vs. Level Sensitive for Internal IRQs

Posted: Wed Dec 08, 2004 9:28 pm
by pfilippi
Dear AT91 Users,

you have probably all noticed that for internal IRQ sources coming from internal peripherals and going to the AIC, there is the possibility to configure the source type as Edge Triggered detection or Level Sensitive detection.

But what is the best one to use :?:

If we take the case that you only have one not nested interrupt at a time to manage in your application (I have a doubt... :shock: ), you can use the edge triggerred mode. But when there are severals IRQs to manage from one peripheral, by using the edge triggered way, you may lose IRQs if the first IRQ has not been treated fast enough to get another one from the same peripheral. The document attached with this topic gives you the explaination. To conclude there is no particular reason to use the edge triggered mode for internal IRQs.

Posted: Fri Oct 20, 2006 7:46 am
by bfdegraaff
Hello Patrick,

Test interrupts with AIC_ISCR can only be set/cleared in edge triggered mode,
so that is one particular use that I know of.

Regards Barry

Re: Edge Triggered vs. Level Sensitive for Internal IRQs

Posted: Tue Jul 06, 2010 4:04 pm
by riceman0
This might or might not be relevant, but here is an issue where I needed edge triggering.

forum/viewtopic.php/f,9/t,19351/

I see what you're saying with the edge triggered IRQs being lost, but I guess my answer is that I would use edge triggered IRQs in any case where (a) I need one-shot functionality and (b) that isn't a concern (which I presume is most of the time).

Re: Edge Triggered vs. Level Sensitive for Internal IRQs

Posted: Tue Jul 06, 2010 6:17 pm
by riceman0
I just noticed that I answered a 5 and a half year old question.

That for some reason is set to "sticky."

And I'm the only reply after 2,956 views.

Conclusion: I really don't get how this forum works.

Re: Edge Triggered vs. Level Sensitive for Internal IRQs

Posted: Wed Jul 07, 2010 12:24 am
by akohlsmith
You saw a 5.5 year old question? I can't seem to access forum topics older than about 30 days. "No such topic exists" type of error.

Re: Edge Triggered vs. Level Sensitive for Internal IRQs

Posted: Wed Jul 07, 2010 1:42 am
by riceman0
I'm talking about this question... you don't see a date of

Wed Dec 08, 2004 9:28 pm

on this post?

I'm also getting the "topic doesn't exist" error.

Re: Edge Triggered vs. Level Sensitive for Internal IRQs

Posted: Wed Jul 07, 2010 1:46 am
by akohlsmith
Yes, I see the same date. I think there's something very wrong with the database this forum uses. Forums as a general rule are awful, awful things. Is there an at91 mailing list?

Re: Edge Triggered vs. Level Sensitive for Internal IRQs

Posted: Wed Jul 07, 2010 1:55 am
by riceman0
Yeah, must be.

However in general I really like forums for technical questions; e.g., experts exchange. Can't find any other live resources for our at91sam9261, so pretty disappointed this one is hosed up.

Re: Edge Triggered vs. Level Sensitive for Internal IRQs

Posted: Wed Jul 07, 2010 1:56 am
by riceman0
That said, I couldn't really get replies to my (probably easy) questions even when things seemed to be working better...

Re: Edge Triggered vs. Level Sensitive for Internal IRQs

Posted: Wed Jul 07, 2010 1:57 am
by riceman0
In fact I think you're the second or third living person I've encountered. I am legend.