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LCD Interfacing To 8051 in 8 bit mode |
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Code Library -
8051 Assembly
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Liquid Crystal Display also called as LCD is very helpful in providing user interface as well as for debugging purpose. The most common type of LCD controller is HITACHI 44780 which provides a simple interface between the controller & an LCD. These LCD's are very simple to interface with the controller as well as are cost effective.
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The LCD requires 3 control lines (RS, R/W & EN) & 8 (or 4) data lines. The number on data lines depends on the mode of operation. If operated in 8-bit mode then 8 data lines plus 3 control lines i.e. total 11 lines are required. Here is a program for interfacing a LCD through 8051 in 8 bit mode.
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The three control lines are RS, RW & Enable.
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RS: Register Select. When RS = 0 the command register is selected. When RS=1 the data register is selected.
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RW: Read or Write. When RW=0 write to LCD. When RW=1 read from LCD.
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Enable: Used to Latch data into the LCD. A HIGH TO LOW edge latches the data into the LCD.
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LCD Interfacing to 8051
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In this program the controller checks the busy flag & waits till the LCD is busy.
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LCD_RS |
BIT |
P2.5 |
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LCD_RW |
BIT |
P2.6 |
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CD_E |
BIT |
P2.7 |
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LCD_pORT |
EQU |
P0 |
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ORG 0000h
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mov a,#38h
call lcd_command
mov a,#06h
call lcd_command
mov a,#0ch
call lcd_command
mov a,#01h
call lcd_command
mov a,#86h
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call lcd_command |
//1st line 6th character |
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mov a,#'D'
call lcd_datadisplay
mov a,#'N'
call lcd_datadisplay
mov a,#'A'
call lcd_datadisplay
mov a,#0c3h
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call lcd_command |
//2nd Line 3rd character |
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mov a,#'T'
call lcd_datadisplay
mov a,#'E'
call lcd_datadisplay
mov a,#'C'
call lcd_datadisplay
mov a,#'H'
call lcd_datadisplay
mov a,#'N'
call lcd_datadisplay
mov a,#'O'
call lcd_datadisplay
mov a,#'L'
call lcd_datadisplay
mov a,#'O'
call lcd_datadisplay
mov a,#'G'
call lcd_datadisplay
mov a,#'Y'
call lcd_datadisplay
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/*
Sends whatever data is in the Acc to the LCD as a Command
*/
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lcd_command: |
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call lcd_ready |
//waits till the LCD is ready |
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mov LCD_PORT,a |
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clr LCD_RW |
//we are writing to LCD so RW=0 |
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clr LCD_RS |
//Data we are sending is a command so RS=0 |
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setb LCD_E |
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clr LCD_E |
//LATCH data onto LCD |
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ret |
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/*
Sends whatever data is in the Acc to the LCD to be displayed
*/
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lcd_datadisplay: |
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call lcd_ready |
//waits till the LCD is ready |
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mov LCD_PORT,a |
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clr LCD_RW |
//we are writing to LCD so RW=0 |
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setb LCD_RS |
//Data we are sending is a command so RS=0 |
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setb LCD_E |
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clr LCD_E |
//LATCH data onto LCD |
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ret |
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/*
This subroutine checks the busy flag & waits till LCD is ready to ready for next instruction
*/
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lcd_ready:
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mov LCD_PORT,#0ffh
clr LCD_RS
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setb LCD_RW |
//we are reading from LCD so RW=1 |
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l1_lcd_ready: |
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clr LCD_E
setb LCD_E
jb LCD_PORT.7,
clr LCD_E
ret
END
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