;**********************************************************************
;   This file is a basic code template for assembly code generation   *
;   on the PICmicro PIC16F877. This file contains the basic code      *
;   building blocks to build upon.                                    *  
;                                                                     *
;   If interrupts are not used all code presented between the ORG     *
;   0x004 directive and the label main can be removed. In addition    *
;   the variable assignments for 'w_temp' and 'status_temp' can       *
;   be removed.                                                       *                         
;                                                                     *
;   Refer to the MPASM User's Guide for additional information on     *
;   features of the assembler (Document DS33014).                     *
;                                                                     *
;   Refer to the respective PICmicro data sheet for additional        *
;   information on the instruction set.                               *
;                                                                     *
;   Template file assembled with MPLAB V4.00 and MPASM V2.20.00.      *
;                                                                     *
;**********************************************************************
;                                                                     *
;    Filename:	    xxx.asm                                           *
;    Date:                                                            *
;    File Version:                                                    *
;                                                                     *
;    Author:                                                          *
;    Company:                                                         *
;                                                                     * 
;                                                                     *
;**********************************************************************
;                                                                     *
;    Files required:                                                  *
;                                                                     *
;                                                                     *
;                                                                     *
;**********************************************************************
;                                                                     *
;    Notes:                                                           *
;                                                                     *
;                                                                     *
;                                                                     *
;                                                                     *
;**********************************************************************


	; list directive to define processor
	list      p=16f877

	; processor specific variable definitions
	include   p16f877.inc
	
	__CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_OFF & _HS_OSC & _WRT_ENABLE_ON & _LVP_OFF & _DEBUG_OFF & _CPD_OFF 

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






;***** VARIABLE DEFINITIONS
w_temp		EQU	0x70		; variable used for context saving 
status_temp	EQU	0x71		; variable used for context saving

ctr0		EQU	0x20
ctr1		EQU	0x21
ctr2		EQU	0x22
work		EQU	0x23





;**********************************************************************
		ORG     0x000		; processor reset vector
		clrf    PCLATH		; ensure page bits are cleared
  		goto    main		; go to beginning of program


		ORG     0x004		; interrupt vector location
		movwf   w_temp		; save off current W register contents
		movf	STATUS,w	; move status register into W register
		movwf	status_temp	; save off contents of STATUS register


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


		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

; remaining code goes here

		bsf 	STATUS,RP0	; access to TRISC
		movlw	0x3f
		movwf	TRISC
		bcf	STATUS,RP0	; access to PORTC

		movlw	0xff
		movwf	PORTC

		movlw	0x80
		movwf	work

mainloop
		movlw	0x12
		movwf	ctr2
loop2
		clrf	ctr1
loop1
		clrf	ctr0
loop
		decf	ctr0,1
		bnz	loop

		decf	ctr1,1
		bnz	loop1

		decf	ctr2,1
		bnz	loop2

		movf	work,0
		movwf	PORTC
		comf	work,1		; toggle led's
		goto	mainloop

		END			; directive 'end of program'