Hi, I am using some bits of code I threw together from your tutorial section. When I run the program the display reads correctly but appears to have a raster scan through the display. When I load up another lcd program I downloaded from a site and it works perfectly.

This leads me to believe my program is software related.

This is the program I pieced together myself. Can anyone advise if the problem is in my code.

Thanks

James Krushlucki



; LCD Example Program
; Works with P1 as data port, R/W connected to P3.2, Enable to P3.4, RS to P3.3
;*****
#INCLUDE "8051EQU.INC" ;include predefined constants
;
;**************************************************************************
; VARIABLES AND CONSTANTS
;
DB0 .EQU P1.0
DB1 .EQU P1.1
DB2 .EQU P1.2
DB3 .EQU P1.3
DB4 .EQU P1.4
DB5 .EQU P1.5
DB6 .EQU P1.6
DB7 .EQU P1.7
EN .EQU P3.4
RS .EQU P3.3
RW .EQU P3.2
DATA .EQU P1
;
;**************************************************************************
;
; RESET ;reset routine
;
.ORG 0H ;locate next command at 00H
AJMP START ;jump to START (first command of program)
;
;**************************************************************************
;
; INTERRUPTS ;place interrupt routines at appropriate
;memory locations
.ORG 03H ;external interrupt 0
RETI
.ORG 0BH ;timer 0 interrupt
RETI
.ORG 13H ;external interrupt 1
RETI
.ORG 1BH ;timer 1 interrupt
RETI
.ORG 23H ;serial port interrupt
RETI
.ORG 2BH ;locate beginning of rest of program
;
;**************************************************************************
;
INITIALIZE: ;set up control registers
;
MOV TCON,#00H
MOV TMOD,#00H
MOV PSW,#00H
MOV IE,#00H ;disable interrupts
RET
;**************************************************************************
INIT_LCD:
;
SETB EN
CLR RS
MOV DATA,#30h ;NUMBER OF LINES, FONT SIZE AND DATA BITS
CLR EN
LCALL WAIT_LCD
SETB EN
CLR RS
MOV DATA,#0Ch ;DISPLAY, CURSOR AND BLINK ON/OFF,
CLR EN
LCALL WAIT_LCD
SETB EN
CLR RS
MOV DATA,#010h ;CURSOR SHIFT, LEFT OR RIGHT
CLR EN
LCALL WAIT_LCD
RET
;
CLEAR_LCD:
;
SETB EN
CLR RS
MOV DATA,#01h
CLR EN
LCALL WAIT_LCD
RET
;
WRITE_TEXT:
;
SETB EN
SETB RS
MOV DATA,A
CLR EN
LCALL WAIT_LCD
RET
;
WAIT_LCD:
;
SETB EN ;Start LCD command
CLR RS ;It's a command
SETB RW ;It's a read command
MOV DATA,#0FFh ;Set all pins to FF initially
MOV A,DATA ;Read the return value
JB ACC.7,WAIT_LCD ;If bit 7 high, LCD still busy
CLR EN ;Finish the command
CLR RW ;Turn off RW for future commands
RET
;
START:
LCALL INITIALIZE
LCALL INIT_LCD
LCALL CLEAR_LCD
MOV A,#'H'
LCALL WRITE_TEXT
MOV A,#'E'
LCALL WRITE_TEXT
MOV A,#'L'
LCALL WRITE_TEXT
MOV A,#'L'
LCALL WRITE_TEXT
MOV A,#'O'
LCALL WRITE_TEXT
MOV A,#' '
LCALL WRITE_TEXT
MOV A,#'W'
LCALL WRITE_TEXT
MOV A,#'O'
LCALL WRITE_TEXT
MOV A,#'R'
LCALL WRITE_TEXT
MOV A,#'L'
LCALL WRITE_TEXT
MOV A,#'D'
LCALL WRITE_TEXT
.END