On Wed, 6 Sep 2000, Thomas C. Sefranek wrote:

> I may have found an obscure bug in the 452.
>
> I am using a Jump table (Vector table) I designed to provide 128 possible
> vectors
> relative to the value of the W (Index).
>
> It works 99% of the time....
>
> BUT, If I get an interupt coincident with the code on line 28:
> MOVFF PCLOW,PCL
> The PIC stack the next address as the return address instead of the address I
> just built!
> So I have a hack fix to keep my program working. (See the next line of code.)
> But I should like to hear from you folks, any ideas?  Is this a genuine bug?
> (Did I miss the warning somewhere?)

yuck.

>
> FIX I made:
> 00021C C01A FFF9  00028 Bug_Fix MOVFF PCLOW,PCL  ; Goto supporting routine for
> this state.
> 000220 EF0E F001    00029                 GOTO    Bug_Fix         ; Hack fix.
>                                    00030 ;
> 000224 0000              00031 MENU_TABLE      DW 0            ; Dummy address.

Another fix would be:

    MOVF  PCLOW,W
    MOVWF PCL

with the side affect that W is trashed.



Scott

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