> > - are you aware of the read-modify-write 'feature'?
> 
> Maybe Nick isn't, and you might have seen something in
> his description that I missed, but it's not *that* clear to me
> that this is a r-m-w problem. In fact, Nick wrote :

>From his discription I was not sure that he was using a shadow, so I'd
better ask.

Using a shadow register and using this (also) in an interrupt has some
'interesting aspects in its own, like

(main)
   movfw SHADOW
   -- interrupt occurs right here
   XORLW 0x01
   movwf SHADOW

(interrupt)
   bsf SHADOW, 7

The bit set in SHADOW by the interrupt will be overwritten by the main
....

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: www.voti.nl
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docent Hogeschool van Utrecht: www.voti.nl/hvu
 

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