One easy way is with jump tables. Works something like this:

        mov ptr, [function number]
        mov w, <<ptr    ; w = 2 * function number
        call function_table

function_table:
        jmp pc+w        ; you ARE allowed to do that;
                        ; you are just adding W to PC
        ; each one of these is 2 words, page (because of @) then jump
        jmp @function0
        jmp @function1
        jmp @function2
        etc.

Then the functions can be written normally. You can probably find some
examples of doing this on 16 series PICs; it works exactly the same,
the assembly syntax is just a little different.

Now since you can add to PC just like any file register you may be
able to just do something like this:
        mov w, callback
        mov pc, w
I'm not sure if that works or not. You could try it in a simulator
if you have one.

Amir Shalem wrote:
>
> is it possible in SX to do CALL or JMP to an address specficed in a
> variable ?
>
> something like this: (this doesn't work)
>
>         callback        EQU     $08
>         reset start
>
> start   mov callback, myfunction
>         call callback
>
> myfunction
>         ;do something
>         ret
>
> In C, its easy to do
>
> void function() { return; }
>
> typedef void (*ptr) (void);
>
> void start() {
>         ptr *pointer;
>
>         pointer = function;
>         (pointer)();
> }
>
> is it possible to do in SX asm ?
>
> thanks,
>         Amir.
>
> --
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