;**********************************************************************
;   This file is a basic code template for object module code         *
;   generation on the PIC16C72. This file contains the                *
;   basic code building blocks to build upon.                         *
;                                                                     *
;   Refer to the MPASM User's Guide for additional information on     *
;   features of the assembler and linker (Document DS33014F).         *
;                                                                     *
;   Refer to the respective PIC data sheet for additional             *
;   information on the instruction set.                               *
;                                                                     *
;**********************************************************************
;                                                                     *
;    Filename:      xxx.asm                                           *
;    Date:                                                            *
;    File Version:                                                    *
;                                                                     *
;    Author:                                                          *
;    Company:                                                         *
;                                                                     * 
;                                                                     *
;**********************************************************************
;                                                                     *
;    Files required: P16C72.INC                                       *
;                                                                     *
;                                                                     *
;                                                                     *
;**********************************************************************
;                                                                     *
;    Notes:                                                           *
;                                                                     *
;                                                                     *
;                                                                     *
;                                                                     *
;**********************************************************************


    list      p=16c72             ; list directive to define processor
    #include <p16c72.inc>         ; processor specific variable definitions
    
    __CONFIG   _CP_OFF & _WDT_ON & _BODEN_ON & _PWRTE_ON & _RC_OSC

; '__CONFIG' directive is used to embed configuration data within .asm file.
; The labels following the directive are located in the respective .inc file.
; See respective data sheet for additional information on configuration word.

;***** VARIABLE DEFINITIONS (examples)

; example of using Uninitialized Data Section
INT_VAR       UDATA     0x20   
w_temp        RES     1           ; variable used for context saving 
status_temp   RES     1           ; variable used for context saving

DUMMY_VAR     UDATA     0xA0
w_temp1       RES     1           ; GPR place holder for context saving
                                  ; if w_temp is reserved at 0x20 then GPR
                                  ; 0xA0 must be reserved as well (interrupts) 

; example of using Overlayed Uninitialized Data Section
; in this example both variables are assigned the same GPR location by linker
G_DATA        UDATA_OVR           ; explicit address can be specified
flag          RES     2           ; temporary variable (shared locations - G_DATA)

G_DATA        UDATA_OVR   
count         RES     2           ; temporary variable (shared locations - G_DATA)

;**********************************************************************
RESET_VECTOR  CODE    0x0000       ; processor reset vector
              goto    start        ; go to beginning of program


INT_VECTOR   CODE    0x0004        ; interrupt vector location

INTERRUPT

        movwf   w_temp            ; save off current W register contents
        movf    STATUS,w          ; move status register into W register
        bcf     STATUS,RP0        ; ensure file register bank set to 0
        movwf   status_temp       ; save off contents of STATUS register

        ; isr code can go here or be located as a call subroutine elsewhere

        bcf     STATUS,RP0        ; ensure file register bank set to 0
        movf    status_temp,w     ; retrieve copy of STATUS register
        movwf   STATUS            ; restore pre-isr STATUS register contents
        swapf   w_temp,f
        swapf   w_temp,w          ; restore pre-isr W register contents
        retfie                    ; return from interrupt

MAIN    CODE

start

        nop                       ; code starts here (example)
        banksel  flag             ; example 
        clrf   flag               ; example

        ; remaining code goes here

        END                      ; directive 'end of program'

