> > You need to save everything you use which the main program might use.
> > So if you use PCLATH then yes you must save it and restore it.
>
>     thanks, it's a good answer... :)
>
>     I've made some experiments and after some thought I'm now using (you
> will find it very similar to the Microchip code on the PICs datasheets):
>
>         #INT_GLOBAL
>         void interrupt(void)
>         {
>             static byte s1_save;
>             static byte s2_save;
>             static byte s3_save;
>
>             #asm
>             // save registers
>             MOVWF s1_save
>             SWAPF STATUS,W
>             BCF   STATUS,RP0
>             BCF   STATUS,RP1
>             MOVWF s2_save
>             MOVF  PCLATH,W
>             MOVWF s3_save
>             CLRF  PCLATH
>             #endasm
>
>             if (INTCON.RTCC) {
>                 INTCON.RTCC = 0;
>                 // do that thing you do...
>             }
>
>             #asm
>             // restore registers
>             BCF   STATUS,RP0
>             BCF   STATUS,RP1
>             MOVF  s3_save,W
>             MOVWF PCLATH
>             SWAPF s2_save,W
>             MOVWF STATUS
>             SWAPF s1_save,F
>             SWAPF s1_save,W
>             #endasm
>         }
>
>     Best regards,
>
>     Brusque

That's okay as long as you check the code produced for the C part of your
routine carefully to make sure it isn't using any other registers.

I would try and do the whole routine in assembler myself so I would know for
sure what registers it used.

Brian Gregory.
briang@cix.compulink.co.uk

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