>>> bcf INTCON,GIE
>>> movfw shadow
>>> movwf PORTx
>>> bsf INTCON,GIE
>>>
>>> The interrupt latency will increase at most by 3 TCy.
>>>     
>> True, but that sequence works only if interrupts were disabled at the 
>> start.
>>   
> If you analyze it well, you may notice that this will work, because the
> bsf is atomic and the ISR must use the shadow the same way the main
> routine does (without the interrupts disabling/enabling of course).

What I meant was that the sequence enables interrupts, even when 
interrupts were initially disabled. Hence it is not Ok for a 
general-purpose 'flush the shadow to the port' routine.

-- 

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu

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