Edge Triggered vs. Level Sensitive for Internal IRQs

pfilippi · **Joined:** Fri Feb 13, 2004 7:53 pm **Posts:** 329

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.

bfdegraaff · **Joined:** Mon Oct 09, 2006 10:23 am **Posts:** 2

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

riceman0 · **Joined:** Mon Jan 11, 2010 4:37 pm **Posts:** 37

This might or might not be relevant, but here is an issue where I needed edge triggering.

http://www.at91.com/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).

riceman0 · **Joined:** Mon Jan 11, 2010 4:37 pm **Posts:** 37

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.

akohlsmith · **Joined:** Sun Jul 04, 2010 10:58 pm **Posts:** 4

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.

riceman0 · **Joined:** Mon Jan 11, 2010 4:37 pm **Posts:** 37

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.

akohlsmith · **Joined:** Sun Jul 04, 2010 10:58 pm **Posts:** 4

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?

riceman0 · **Joined:** Mon Jan 11, 2010 4:37 pm **Posts:** 37

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.

riceman0 · **Joined:** Mon Jan 11, 2010 4:37 pm **Posts:** 37

That said, I couldn't really get replies to my (probably easy) questions even when things seemed to be working better...

riceman0 · **Joined:** Mon Jan 11, 2010 4:37 pm **Posts:** 37

In fact I think you're the second or third living person I've encountered. I am legend.

Edge Triggered vs. Level Sensitive for Internal IRQs

Who is online