Flavio Cappelli wrote:

>Hello All,
>I need to have autoincrement enabled and I need double indirect
>addressing (to get a pointer in a vector of pointers). Can I use this ?
>
>movfp index,FSR0
>movfp INDF0, FSR0
>
>or autoincrement modifies FSR0 after last instruction ?
>In this case I should resolve with:
>
>movfp index, FSR0
>movfp INDF0, WREG
>movfp WREG, FSR0
>
>Can anybody confirm this ?
>Tanks in advance.


It does not work. The instruction "movfp INDF0, FSR0" writes the value of
INDF0 to index; since the INDF0 file is not phisically implemented, it is read
as "0", according with the data sheet, then this instruction indirectly writes
a "0" to the "index" location.
If you want to get a pointer in a pointer array, you must add the list number
of the pointer to the pointer array's base, then transfer that value to FSR0,
then read INDF0, something like this:

movfp index,WREG                ; index is the position of the pointer in the ar
ray, I
                                                ;assume 8-bit pointers
addlw pointer_base              ; pointer_base is the address of the first point
er in the
                                                ;array, i.e., the address of the
 array
movwf FSR0
movpf INDF0, WREG               ; WREG is loaded with the desired pointer

If you now need to recover the value of the location this pointer addresses
to, you must

movwf FSR0
movpf INDF0,WREG                ; result is in WREG

This works even if autoincrement is enabled, but take into account that the
final value of FSR0 may be different from the value you need; if so, you must
save it before this chunk of program, and restore after.

Regards

Leonardo Perretti
l.perretti@isnet.it