;**********************************************************************
;   This file is a basic code template for assembly code generation   *
;   on the PICmicro PIC16F876. 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      p=16f876            ; list directive to define processor
	#include <p16f876.inc>        ; processor specific variable definitions
	
;	__CONFIG _CP_OFF & _WDT_ON & _BODEN_ON & _PWRTE_ON & _RC_OSC & _WRT_ENABLE_ON & _LVP_ON & _DEGUB_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
TEMP1	equ	0x20		;Temp variables
TEMP2	equ	0x21
TEMP3	equ	0x22





;**********************************************************************
		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



main
	CLRF STATUS			; Bank0
	CLRF PORTB 			; Initialize PORTB by clearing output
					; data latches
	BSF STATUS, RP0 		; Select Bank1
	MOVLW 0xE1 			; Value used to initialize data direction
	MOVWF TRISB 			; E1 :11100001 - CF PORTB<3:0> = inputs, PORTB<5:4> = outputs
					; PORTB<7:6> = inputs
	BCF STATUS, RP0


; remaining code goes here


	CLRF STATUS
LOOP
	MOVLW 0x10
	MOVWF PORTB
	call	DELAY
	
	MOVLW 0x08
	MOVWF PORTB
	call	DELAY
	
	MOVLW 0x04
	MOVWF PORTB
	call	DELAY
	
	MOVLW 0x02
	MOVWF PORTB
	call	DELAY
	
	goto	LOOP			;Repeat

;***************************************
;*  This routine is a software delay.  *
;*  Fosc = 1/Tosc; Tcycle = 4 x Tosc   *
;*  Delay = TEMP1xTEMP2xTEMP3xTcycle   *
;***************************************

DELAY

	movlw	0xFF 
	movwf	TEMP1			;TEMP1 = 255
	movwf	TEMP2			;TEMP2 = 255
	movlw	0x07 
	movwf	TEMP3			;TEMP3 = 7

DLOOP
	decfsz  TEMP1, F
	goto    DLOOP

	decfsz  TEMP2, F
	goto    DLOOP

	decfsz  TEMP3, F
	goto    DLOOP

	retlw	0x00

		END                       ; directive 'end of program'