TONY NIXON 54964 <PICLIST@MITVMA.MIT.EDU> wrote:

> What if [an interrupt occurs when] the current instruction is
> 'ADDWF PCL', as in a jump table.
>
> The program counter word would now become
>
> Hi Byte = Pclath<4:0>    Low Byte = PCL + W.
>
> Does the interupt preserve this as it's return address, or does it
> point to the next address as it normally would.

    Tony:

    There's an appnote from Microchip (AN556) that says you need to
    disable interrupts around computed jumps.

    The appnote is WRONG.

    In the situation you describe, everything will work perfectly;
    when the PIC returns from servicing the interrupt, the PC will
    be at the correct location in your lookup table or whatever.

    -Andy

=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering, Vista, California
=== http://www.geocities.com/SiliconValley/2499