On Thu, Mar 10, 2011 at 11:04 AM, Olin Lathrop
<olin_piclist@embedinc.com> wrote:
> Josh Koffman wrote:
>> For WREG, on entry I execute a
>> "MOVWF =A0 =A0 W_Temp", and on exit "MOVF =A0 =A0 W_Temp, W".
>
> That will trash some status bits.
>
> <rant>I don't get it. =A0Interrupt save/restore is a well-invented wheel.=
 =A0Why
> do people keep trying to create their own code, especially when they don'=
t
> know what they're doing enough to get it right!?</rant>

Actually, I didn't invent it. It's come from numerous examples online
and in the datasheets. In this case, it's datasheet 39689f.pdf, page
109, example 10-1. I didn't copy and paste the entire routing the
first time because I didn't think it was relevant. Evidently I was
incorrect. Here it is:

Interrupt
     movwf	     W_Temp                   ; Save context during low interrup=
t
     movff       STATUS, STATUS_Temp =09
     movff       BSR, BSR_Temp	=09

<ISR CODE HERE>

     movff       BSR_Temp, BSR      ; Restore context saved above
     movf        W_Temp, W
     movff       STATUS_Temp, STATUS
     RETFIE


Josh
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