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

Thu Jan 19 2017, 08:42 PM
abhays
Hi...i have made a circuit for interfacing PT100 with LM358 whose temperature is shown on the LCD...But the temperature is not getting incresed slowly ..a small change directly increses the temp...can any one help me
Thu Jan 19 2017, 04:27 PM
roba
send me alarm clock simulation using proteus software
Mon Jan 16 2017, 03:15 PM
Rutuja
How can we read notepad file using random acess file
Fri Jan 06 2017, 06:18 AM
muhammad Umar
i need cd4047 library file for protious please help me i s
ExperimenterUK
Wed Jan 04 2017, 09:01 PM
@Emin what is your site user name ?
Tue Jan 03 2017, 11:16 PM
Emin
Emin: I'm already a member since 2012 and entered repeatedly during period. But now it is impossible and obtaining a new registration is also failed. The same error message specifying that two e-mails i entered are different!. In fact thaey are the same. Now, what will be happen, what is your solution? Thanks..
Tue Jan 03 2017, 11:15 PM
Emin
I'm already a member since 2012 and entered repeatedly during period. But now it is impossible and obtaining a new registration is also failed. The same error message specifying that two e-mails i entered are different!. In fact thaey are the same. Now, what will be happen, what is your solution? Thanks..
Sun Jan 01 2017, 03:14 PM
Manoranjana Chary
Write an embedded program of increment and decrement in LCD connected to two keys of int1 and int0. Can u please send me the code for this as fast as possible because i need to submit it in college kindly
ExperimenterUK
Sat Dec 31 2016, 06:28 PM
Happy New Year everyone
ExperimenterUK
Sat Dec 31 2016, 06:27 PM
Please post questions in the forum, the chat box is for chat

Downloads

Comments

jmunjr
Tue Jan 17 2017, 06:25 PM
sarfrosh92
Sun Jan 15 2017, 09:18 AM
Deepakvaishu
Wed Jan 11 2017, 10:25 AM
rana_jee773
Sat Dec 10 2016, 11:22 AM
[email protected]
Thu Dec 08 2016, 11:02 AM
Jonathan.kei
Mon Nov 21 2016, 04:30 PM
AVRuser1
Sun Nov 20 2016, 06:07 PM
JaguarPaw
Thu Nov 17 2016, 07:44 PM

Online

Guests: 42, Members: 0 ...

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

Members: 37797
Newest member: jmunjr
Forum Activity
ExperimenterUK Avatar
Posted By ExperimenterUK
Sat Jan 21 2017, 06:48 AM
I should say that setting up CODE::BLOCKS (or any...
Deepakvaishu Avatar
Posted By Deepakvaishu
Sat Jan 21 2017, 04:42 AM
Thanks a lot..I will try with SDCC, or else I will...
ExperimenterUK Avatar
Posted By ExperimenterUK
Fri Jan 20 2017, 09:35 PM
SDCC is a compiler, it turns text (source code) in...
sankalp_s Avatar
Posted By sankalp_s
Fri Jan 20 2017, 04:40 PM
Thank you so much sir for your great response.. :)...
Deepakvaishu Avatar
Posted By Deepakvaishu
Fri Jan 20 2017, 08:47 AM
Is the steps of programmming of keil and sdcc sa...
ExperimenterUK Avatar
Posted By ExperimenterUK
Fri Jan 20 2017, 12:50 AM
Looks like you are using a demo version of Keil.Ei...
ExperimenterUK Avatar
Posted By ExperimenterUK
Fri Jan 20 2017, 12:31 AM
The original reverse24displayloop:was a bit messy....
sankalp_s Avatar
Posted By sankalp_s
Thu Jan 19 2017, 05:52 PM
Thank you sir.. understood the logic..But reverse ...
Deepakvaishu Avatar
Posted By Deepakvaishu
Thu Jan 19 2017, 09:48 AM
my code is working now..But the next problem which...
Deepakvaishu Avatar
Posted By Deepakvaishu
Thu Jan 19 2017, 04:50 AM
I am using serial interrupt for RFID card reader,...