> In the PICUART.ASM document/source by T. McGahee, there
> is discussion about clearing GIE by doing like this :
>
> goe01   bcf    intcon, gie
>         btfsc  intcon, gie
>         goto   gie01
>
> Se the document for the reason to do this. It has something
> to do with an interupt occuring *during* the execution of
> the BCF intruction.

Some 16 family PICs had a bug where an interrupt could be taken right
after the GIE bit was cleared by BCF INTCON,GIE.  The RETFIE at the end of
the interrupt routine would re-enable interrupts.  The net effect is that
BCF INTCON,GIE disabled interrupts most of the time but not always.  The
workaround was to test the bit and try to clear it again if it was still
set.

See my INTR_OFF macro in STD.INS.ASPIC at http://www.embedinc.com/pic.  It
emits the workaround code on those chips with the bug, and a simple BCF
INTCON,GIE on others.  It also handles the different details of disabling
interrupts on the 17 and 18 family.


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