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'[PIC] Concurrency of CCP & Timer1 interrupt'
2005\05\08@113152 by Zhaoyue Wang

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Hi.

I use ccp and timer1 to capture external signal, the period of the signal is larger than  timer1's.
So timer1 will timeout during capture.
My question is if ccp capture external signal and at the same time timer1 timeout,  then both interrupt flag
will be set, or the TMR1IF is set earlier or else?

I use pic16f877.

thx.

zhaoyue wang

2005\05\08@155059 by Jan-Erik Soderholm

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Zhaoyue Wang wrote :

> My question is if ccp capture external signal and at the same
> time timer1 timeout,  then both interrupt flag
> will be set,

Yes.

> or the TMR1IF is set earlier or else?

Might be set earlier or later, that depends on *when* the two
interrupt happens, but TMR1IF will not prevent any other
xxxxIF flagt be set. There are no cross-dependences
between the xxxxIF flags.

Just remember to check *which* xxxxIF got you into the ISR !!

And at the end of your ISR, *only* clear the IF that you have
just served! I have seen ISR's that, at the end, cleared multiple
IF flags, and then missed any interrupt (other then the currently
served) that had fired during the current execution of the ISR...

Jan-Erik.



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