On Sat, 9 Aug 2003 23:51:13 -0600, Steve wrote:

>Hi Ken,
>
>W is used to pass data to LCD_Data. The interrupt service uses the following to
>prevent it from currupting other operations.
>
> movwf  w_int                     ;save w
> movf   STATUS,w                ;save STATUS
> movwf  Stat_int
> movf   FSR,w                   ;save FSR
> movwf  FSR_int
><<< service here >>>
> movf   FSR_int,w
> movwf  FSR
> movf   Stat_int,w
> movwf  STATUS
> movf   w_int,w                   ;restore w
> bcf    STATUS,Z                ;ensure that restoring w
> btfsc  Stat_int,Z              ;does not change zero flag state
>  bsf   STATUS,Z
>

I've lost track of which processor you're using but something doesn't
look right with your restore. Microchip's example code uses SWAPF to
save and restore the STATUS register.

You may want to check the datasheet under Special Features section.

Are all of your save and restore locations in the same bank? You may
not be using the banks that you think you are.

Any pending interrupt will occur as soon as you set GIE so you
probably have a higher chance of taking an interrupt on your way to
the LCD routine.


Regards, Bob

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