4-bit Initialization

Initialization of LCD is completed only after the reset sequence and basic initialization commands. We have already discussed about the reset sequence of the lcd in the previous section. So lets look at the programming now...

Assembly Program
;In this whole 4-bit tutorial LCD is connected to
;my controller in following way...
;D4 - P3.0
;D5 - P3.1
;D6 - P3.2
;D7 - P3.3
;EN - P3.7
;RS - P3.5

	lcd_port equ P3         ;LCD connected to Port3
	en equ P3.7             ;Enable connected to P3.7
	rs equ P3.5             ;Register select to P3.5
	
lcd_reset:                  ;LCD reset sequence
	mov lcd_port, #0FFH
	mov delay,#20           ;20mS delay
	acall delayms
	mov lcd_port, #83H      ;Data = 30H, EN = 1, First Init
	mov lcd_port, #03H      ;Data = 30H, EN = 0
	mov delay,#15           ;Delay 15mS
	acall delayms
	mov lcd_port, #83H      ;Second Init, Data = 30H, EN = 1

	mov lcd_port, #03H      ;Data = 30H, EN = 0
	mov delay,#5            ;Delay 5mS
	acall delayms
	mov lcd_port, #83H      ;Third Init

	mov lcd_port, #03H
	mov delay,#5            ;Delay 5mS
	acall delayms
	mov lcd_port, #82H      ;Select Data width (20H for 4bit)

	mov lcd_port, #02H      ;Data = 20H, EN = 0
	mov delay,#5            ;Delay 5mS
	acall delayms
	ret


lcd_init:
	acall lcd_reset         ;Call LCD Reset sequence
	mov a,#28H              ;4-bit, 2 line, 5x7 dots

	acall lcd_cmd           ;Call LCD command
	mov a,#0CH              ;Display ON cursor OFF
	acall lcd_cmd           ;Call LCD command
	mov a,#06H              ;Set entry mode (Auto increment)

	acall lcd_cmd           ;Call LCD command
	mov a,#80H              ;Bring cursor to line 1
	acall lcd_cmd           ;Call LCD command
	ret

C Program
//The pins used are same as explained earlier
#define lcd_port    P3

//LCD Registers addresses
#define LCD_EN      0x80
#define LCD_RS      0x20

void lcd_reset()
{
	lcd_port = 0xFF;
	delayms(20);
	lcd_port = 0x03+LCD_EN;
	lcd_port = 0x03;
	delayms(10);
	lcd_port = 0x03+LCD_EN;
	lcd_port = 0x03;
	delayms(1);
	lcd_port = 0x03+LCD_EN;
	lcd_port = 0x03;
	delayms(1);
	lcd_port = 0x02+LCD_EN;
	lcd_port = 0x02;
	delayms(1);
}

void lcd_init ()
{
	lcd_reset();         // Call LCD reset
	lcd_cmd(0x28);       // 4-bit mode - 2 line - 5x7 font. 
	lcd_cmd(0x0C);       // Display no cursor - no blink.
	lcd_cmd(0x06);       // Automatic Increment - No Display shift.
	lcd_cmd(0x80);       // Address DDRAM with 0 offset 80h.
 }

Sending Dommand/Data to LCD in 4-bit mode

Assembly Program
lcd_cmd:                  ;LCD command Routine
	mov temp,a            ;Save a copy of command to temp
	swap a                ;Swap to use higher nibble
	anl a,#0FH            ;Mask the first four bits
	add a,#80H            ;Enable = 1, RS = 0
	mov lcd_port,a        ;Move it to lcd port
	anl a,#0FH            ;Enable = 0, RS = 0
	mov lcd_port,a        ;Move to lcd port

	mov a,temp            ;Reload the command from temp
	anl a,#0FH            ;Mask first four bits
	add a,#80H            ;Enable = 1
	mov lcd_port,a        ;Move to port
	anl a,#0FH            ;Enable = 0
	mov lcd_port,a        ;Move to lcd port

	mov delay,#1          ;delay 1 ms
	acall delayms
	ret

lcd_dat:                  ;LCD data Routine
	mov temp,a            ;Keep copy of data in temp
	swap a                ;We need higher nibble
	anl a,#0FH            ;Mask first four bits
	add a,#0A0H           ;Enable = 1, RS = 1
	mov lcd_port,a        ;Move to lcd port
	nop
	clr en                ;Enable = 0

	mov a,temp            ;Reload the data from temp
	anl a,#0FH            ;we need lower nibble now
	add a,#0A0H           ;Enable = 1, RS = 1
	mov lcd_port,a        ;Move to lcd port
	nop
	clr en                ;Enable = 0

	mov delay,#1          ;Delay 1mS
	acall delayms
	ret

C Program
void lcd_cmd (char cmd)
{ 
	lcd_port = ((cmd >
>
 4) & 0x0F)|LCD_EN;
	lcd_port = ((cmd >
>
 4) & 0x0F);

	lcd_port = (cmd & 0x0F)|LCD_EN;
	lcd_port = (cmd & 0x0F);

	delayus(200);
	delayus(200);
}

void lcd_data (unsigned char dat)
{ 
	lcd_port = (((dat >
>
 4) & 0x0F)|LCD_EN|LCD_RS);
	lcd_port = (((dat >
>
 4) & 0x0F)|LCD_RS);
	
	lcd_port = ((dat & 0x0F)|LCD_EN|LCD_RS);
	lcd_port = ((dat & 0x0F)|LCD_RS);

	delayus(200);
	delayus(200);
}

Share it! Like it!

Conversation

ajay_bhargav
Tue Mar 31 2015, 04:14 AM
@Peter james, we have many projects related to this, Please refer download section and tutorials or post in forum for specific questions.
Mon Mar 30 2015, 04:51 PM
Peter james
can any one provide me an assembly language program to interface with 16x2 LCD, 4X4 Keypad and a GSM Module to recieve message and display it.
ajay_bhargav
Mon Mar 23 2015, 04:22 AM
You can only simulate simple 8051. RD2 support is not there in proteus. However there are similar atmel varient which can be used instead.
Sun Mar 22 2015, 07:24 PM
Aryan Nath
How can i Simulate microcontroller project in Proteus that uses P89V51RD2
Thu Mar 19 2015, 02:45 PM
Peter Mann
I have tried to register on the site, but it keeps saying I've entered two different email adresses - but I haven't!
ajay_bhargav
Sun Mar 15 2015, 08:25 PM
I did not get new message indication.. strange..
ExperimenterUK
Sun Mar 15 2015, 08:18 PM
slight delay, my connection failed
ajay_bhargav
Sun Mar 15 2015, 08:08 PM
Atleast you chat on our website if not anywhere else
ajay_bhargav
Sun Mar 15 2015, 08:08 PM
Hi Phil..
ExperimenterUK
Sun Mar 15 2015, 08:05 PM
Hi Ajay

Downloads

Comments

harix
Sun Mar 29 2015, 07:11 PM
marti
Fri Mar 27 2015, 03:07 PM
iamalien
Thu Mar 26 2015, 07:27 AM
Ankit30
Wed Mar 25 2015, 02:35 PM
wai1023
Wed Mar 25 2015, 06:27 AM
StrangerDanger
Tue Mar 24 2015, 12:40 PM
vinayas9
Tue Mar 24 2015, 09:26 AM
ganesh1991
Tue Mar 24 2015, 08:22 AM

Online

Guests: 43, Members: 0 ...

most ever online: 182184
(Members: , Guests: 182184) on 06 Aug 2010: 05:37 AM

Members: 37611
Newest member: harix
Forum Activity
mayank058 Avatar
Posted By mayank058
Tue Mar 31 2015, 06:33 AM
Thanks to all of u for showing your interest in my...
iamalien Avatar
Posted By iamalien
Tue Mar 31 2015, 04:43 AM
here you go a 227 variable array in the ram and st...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Mar 31 2015, 04:33 AM
Can you post Keil compiler output?
iamalien Avatar
Posted By iamalien
Tue Mar 31 2015, 04:31 AM
i have already compiled the program in keil thats ...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Mar 31 2015, 04:29 AM
Its in nature of resistor to reduce the current wh...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Mar 31 2015, 04:10 AM
256 bytes ram for 200 char display... I think you ...
diana1234 Avatar
Posted By diana1234
Mon Mar 30 2015, 08:12 AM
Dear sir,How a resistor can be used as a current l...
ExperimenterUK Avatar
Posted By ExperimenterUK
Mon Mar 30 2015, 05:13 AM
The processor on the MCB2300 has a built in DAC.Cr...
iamalien Avatar
Posted By iamalien
Sun Mar 29 2015, 07:46 PM
yes either that or use the flash reprogrammable va...
ajay_bhargav Avatar
Posted By ajay_bhargav
Sun Mar 29 2015, 07:37 PM
Correct, you cannot change ROM, but you can still ...