Thus spake TONY NIXON 54964 (Anthony.NIXON@ENG.MONASH.EDU.AU):

> What if 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.

The ADDWF to the PC will take 2 cycles, rather than the normal
1, and the interrupt will not be taken until the end of the
instruction, by which time the PC (hi and low) has been updated
to point to the new location in the jump table.

If you are asking "can an interrupt at the wrong time screw things
up" the answer is no - providing the interrupt routine properly
saves and restores any resources used, there will be no effect
on the interrupted code other than the time delay, vicious rumours
(and incorrect data sheets) to the contrary notwithstanding.

--
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clyde@htsoft.com      | P.O. Box 103, Alderley, | Fax:   +61 7 3354 2422
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