Commutation, C interrupt and C event

Posted on May 17, 2011 at 10:19

Hi, All.

Do commutation and C interrupt occure simultaneously?

I make my question a little bit clear using next example.

Let suppose at the certain time some 3 soft priority level ISR runs. At this time MTIM rolles over MCOMP value. Let say C int has 2 soft priority level what causes pending of C int.

My question is folowing : whether real commutation occures exactly at the time when MTIM rolles over MCOMP or when C int ISR starts? And what do MCDEM and MCZEM pins show: commutation or start of ISR processing?

Tnx.

[ This message was edited by: Luter on 23-11-2005 08:42 ]

Posted on May 17, 2011 at 10:19

Ciao Luter,

you are perfectly right!!.

Actually, the debug pins MCZEM and MCDEM were introduced on ST7FMC to show the exact instant when a C, D or Z event occure. This occurence is totally uncorreleted with the execution of related ISR. Moreover, a C, D and Z event cannot be masked anyway, whereas the related ISR execution can be masked acting on mask bit register.

Best regards,

Tanio

Posted on May 17, 2011 at 10:19

According to my investigation Commutation and start of ISR are different events. it means Commutation can occure earlier than ISR starts. MCZEM and MCDEM pins shows commutation events.

But i would like to hear an opinion of the expert to be 100% sure.