Microchip 16F877 Tlcd.asm

; 
	Title "LCD test."
;
	list P = 16F877
;
	include "P16f877.inc"

        __CONFIG _CP_OFF & _WDT_OFF & _BODEN_ON & _PWRTE_ON & _HS_OSC & _WRT_ENABLE_ON & _LVP_ON & _DEBUG_OFF & _CPD_OFF

;
; --------------------
; USER RAM DEFINITIONS
; --------------------
;
	CBLOCK 0x20
;
MessPt
DisData
DelayL
DelayM
DelayH
Temp
;
	ENDC

lcdRW	equ 2h		; RB2 = LCD RW pin
lcdRS	equ 4h		; RB4 = LCD RS pin
lcdE	equ 5h		; RB5 = LCD E pin

; PORTD USED FOR LCD DATA PINS RB0 - RB7 = D0 - D7

;
; ---------------------
; YOUR CODE BEGINS HERE
; ---------------------
;
	org 0x0000

	clrf PORTA
	clrf PORTD
	clrf PORTC
	clrf PORTD
	clrf PORTE
	bsf STATUS,RP0		; RAM Page 1
	clrf TRISA
	clrf TRISB
	clrf TRISC
	clrf TRISD
	clrf TRISE
;
; -------------------------
; SET ANALOG/DIGITAL INPUTS
; -------------------------
;
	movlw b'00000110'		; = all digital
	movwf ADCON1

	bcf STATUS,RP0

	movlw 20h			; 25mS powerup delay @ 4MHz
	movwf DelayH		; data sheet says 15mS
	clrf DelayL
PUPD	decfsz DelayL
	goto PUPD
	decfsz DelayH
	goto PUPD

          call Control        	; initialize display
;
; -----------------------------------------------------
; DISPLAY THE MESSAGE WHEN THE BUTTON ON RA3 IS PRESSED
; -----------------------------------------------------
;
MnLoop	clrf MessPt
	movlw 0x80		; line 1
	call LCDins
Loop1	call TheText
	xorlw 0h
	btfsc STATUS,Z
	goto DoLine2

	call LCDout
	incf MessPt
	goto Loop1

DoLine2	incf MessPt
	movlw 0xC0		; line 2
	call LCDins
Loop2	call TheText
	xorlw 0h
	btfsc STATUS,Z
	goto DoDelay

	call LCDout
	incf MessPt
	goto Loop2

DoDelay	call BigDel		; wait
	goto MnLoop
;
; ------------------------
; LCD INITIALIZATION CODES
; ------------------------
;
TheText	movlw High($)
	movwf PCLATH
	movf MessPt,W
	addwf PCL
	DT "   HELLO FROM", 0h
	DT " THE PIC 16F873", 0h
;
; -----------------
; SEND CONTROL DATA
; -----------------
; According to the data sheet, a delay of 4mS minimum must occur 
; between each control data byte being sent.
;
Control   movlw 38h           ; (128) display initialisation
	call LCDins         ; output to display
          movlw 38h		; page 45 of the data sheet
	call LCDins         ; output to display
          movlw 38h           ; two line
	call LCDins         ; output to display
          movlw .6            ; increment display
	call LCDins         ; output to display
          movlw 0ch           ; display = on, cursor = off
	call LCDins         ; output to display
          movlw .1            ; clear display
          call LCDins         ; output to display
	return
;
; -----------------------------
; OUTPUT 1 DATA BYTE TO DISPLAY
; -----------------------------
;
LCDout    movf DisData,w
          movwf PORTD
          bsf PORTB,lcdRS     ; (4) Write data to display
          call Clock
          bsf PORTB,lcdE      ; (5) enable
          call Clock
          bcf PORTB,lcdE      ; (5)
          call Clock
          bcf PORTB,lcdRS     ; (5)
          bcf STATUS,RP0      ; ram page 0
          return
;
; ------------------------------------
; OUTPUT 1 INSTRUCTION BYTE TO DISPLAY
; ------------------------------------
;
LCDins    movf DisData,w
          movwf PORTD
          bcf PORTB,lcdRS     ; (4) Write instruction to display
          call Clock
          bsf PORTB,lcdE      ; (5) enable
          call Clock
          bcf PORTB,lcdE      ; (5)
          call Clock

	clrf DelayL
	movlw 8h		; about 6mS delay @ 4MHz
	movwf DelayH
ctlp1     decfsz DelayL
          goto ctlp1
	decfsz DelayH
	goto ctlp1

          return
;
; -----------------------------
; CLOCKING DELAY - 200uS @ 4MHz
; -----------------------------
;
Clock	movlw 40h
	movwf DelayL
kdloop    decfsz DelayL
          goto kdloop
          return
;
; --------------------------------
; ABOUT A HALF SECOND DELAY @ 4MHz
; --------------------------------
;
BigDel	clrf DelayL
	clrf DelayM
	movlw 5h
	movwf DelayH
BDloop	decfsz DelayL
	goto BDloop
	decfsz DelayM
	goto BDloop
	decfsz DelayH
	goto BDloop
	return
test	movlw 8h
	movwf DelayH
ctlp2     decfsz DelayL
          goto ctlp2
	decfsz DelayH
	goto ctlp2
	return
;
; -----------------------
; BOOT CODE START ADDRESS
; -----------------------
; DO NOT PLACE ANY CODE PAST THIS POINT
;
	org 0x0F00
;
;
	end

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