----- Original Message -----
From: "Peter L. Peres" <plp@ACTCOM.CO.IL>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, December 24, 2001 11:51 AM
Subject: Re: [PIC]: Implementing MCLR in software


> Hi Wouter, thanks for the ideas, are you trying to say that something like
> this will work ?:
>
> main:
>   bsf STATUS,RP0
>   clrf TRISA
>   bcf STATUS,RP0
>
>   call Thesub           ; call it and then fall through into it
>
> Thesub:
>   movlw 0x01
>   xorwf PORTA,f
>   retlw 0               ; this should jump to Thesub according to your
>                         ; description (pop keeps popping the last value)
>
> BTW I bet a small sum of money that most simulators do not follow this
> functionality. As to usefullness ? Every merchandise has its buyer [tm].
>
> Peter
>

Peter,

This sample will NOT work because only one entry on the stack has been
initialized
to contain the return address that gets you back to 'Thesub'.

This ugly code would work however (assuming interrupts are off):

main:
    bsf    STATUS,RP0
    clrf    TRISA
    bcf    STATUS,RP0
    clrf    COUNTER
Docall:
    call    Thesub
Thesub:
    btfsc    COUNTER,5    ; Have we already filled the stack?
    goto     CountDone       ; Yes
    incf       COUNTER      ; No, count one more
    goto      Docall              ; ...and push another level
CountDone:
    movlw    1
    xorwf     PORTA,F
    retlw      0                    ; will return to ''Thesub' forever


    incfsz    COUNTER,F    ; Bump the counter
    goto      Docall               ; D

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.