"StakCall" Experiment

A Stack using the FSR can be used to pass data to and from subroutines in the PICmicro as is shown in this application.

The source code listed below can be accessed from the CD-ROM by clicking Here.

 title  "StakCall - Passing Subroutine Parms via Stack"
;
;  This Program shows how to set up a psuedo-Stack and use it to pass
;   Parameters between the Mainline and Routines.
;
;  99.11.13 - Updated for Second Edition
;
;  Myke Predko
;  96.05.10
;
  LIST P=16F84, F=INHX8M, R=DEC
  INCLUDE "p16f84.inc"

;  Registers
i     equ 12                    ;  Registers to Operate on
j     equ 13
Stack equ 14                    ;  Start of the virtual Stack

 __CONFIG _CP_OFF & _WDT_OFF & _RC_OSC

  PAGE
;  Mainline of StakCall

  org 0

  movlw  4                      ;  Initialized the Variables
  movwf  i

  movlw  Stack                  ;  Set up the Stack
  movwf  FSR

;  j = Increment( i )

;  Get the value of i + 1 and put it in "j"

  incf   FSR, f                 ;  Make Space for the Sum

  movf   i, w                   ;  Get First Value to Add and store on
  movwf  INDF                   ;   the Stack
  incf   FSR, f

  call   Increment              ;  Increment the Value

  decf   FSR, f                 ;  Get and Store the Sum
  movf   INDF, w
  movwf  j

Finished                        ;  Finished, Just Loop Around Forever
  goto  $

;  Increment Subroutine

Increment                       ;  Add the Two Values on the Stack

  decf   FSR, f                 ;  Get the First Value and Increment it
  incf   INDF, w

  decf   FSR, f                 ;  Store the result
  movwf  INDF

  incf   FSR, f                 ;  Reset the Stack Pointer

  return

  end

Click Here to look at the thirteenth experiment - CallBUp