Hi all,

Still no answer...
I've searched around a bit and found that IOC generates many 
questions from programmers... Most of them on how to use IOC, a few on
reliability of IOC; some answers are speaking of specific software tricks to
workaround hardware "bugs" issues... Something to be scared of...

Maybe a bit of more detailed explanation of what I want to do may help to
understand my questions:
I would want to measure the width of continuous streams of pulses that 
come asynchronously to each other on 10 input pins. 
I dedicated PORTA/PORTB to this. 
Each pulse is say, like a RC model pulse 1-2 ms / 20 ms. 
The idea was, using TMR1 that is let running free, to measure pulse width
on each channel by computing TMR1 delta value between rising and falling 
edges of the signals. 
Some jitter is acceptable (variable latency due to other interrupts) and
would 
be filtered out after. 
It is easy to understand that I cannot miss any signal edge.

I've tried some simple IOC mechanism before one one port only, without 
problems (well, I don't perform a long reliability test...), despite of what 
MC seems to say (see below). 
My question is about using two ports simultaneously. 
I detected some possible problematic points.
Before starting to make an heavy test stand to check this with several 
asynchronous input streams, I would want to know if this approach is 
realistic or not...

Also one other confusing thing for me, as I said in my OP is:

In the PIC16F690 datasheet, Microchip wrote:
> 
> "If a change on the I/O pin should occur when the read operation is being 
> executed (start of the Q2 cycle), then the RABIF interrupt flag may not
> get set."
> 

So the question is still: can we do reliable IOC in all cases? 
This sort of "small print" MC sentence seems to say NO even for a single
bit. 
That's what is boring me.





-----
Best regards,

Philippe.

http://www.pmpcomp.fr Pic Micro Pascal for all! 
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