INTERFACING OF LCD WITH 89C51

Liquid crystal display is very commonly used electronic display module and having a wide range of applications such as calculators, laptops, mobile phones etc. 16×2 character lcd display is very basic module which is commonly used in electronics devices and projects. It can display 2 lines of 16 characters.

Pinout and Pin Description of 16x2 LCD Module

Pin No	Function	Name
1	Ground (0V)	Ground
2	Supply voltage; 5V (4.7V – 5.3V)	Vcc
3	Contrast adjustment; through a variable resistor	VEE
4	Selects command register when low; and data register when high	Register Select
5	Low to write to the register; High to read from the register	Read/write
6	Sends data to data pins when a high to low pulse is given	Enable
7	8-bit data pins	DB0
8		DB1
9		DB2
10		DB3
11		DB4
12		DB5
13		DB6
14		DB7
15	Backlight VCC (5V)	Led+
16	Backlight Ground (0V)	Led-

RS(Register select)

A 16X2 LCD has two registers, namely, command and data. The register select is used to switch from one register to other. RS=0 for command register, whereas RS=1 for data register.

Command Register: The command register stores the command instructions given to the LCD. A command is an instruction given to LCD to do a predefined task like initializing it, clearing its screen, setting the cursor position, controlling display etc. Processing for commands happen in the command register.

Data Register:  The data register stores the data to be displayed on the LCD. The data is the ASCII value of the character to be displayed on the LCD. When we send data to LCD it goes to the data register and is processed there. When RS=1, data register is selected.

Important command codes for LCD

Code (Hex)	working of lcd commands
1	Clear display screen
2	Return home
4	Decrement cursor (shift cursor to left)
6	Increment cursor (shift cursor to right)
5	Shift display right
7	Shift display left
8	Display off, cursor off
A	Display off, cursor on
C	Display on, cursor off
E	Display on, cursor blinking
F	Display on, cursor blinking
10	Shift cursor position to left
14	Shift cursor position to right
18	Shift the entire display to the left
1C	Shift the entire display to the right
80	Force cursor to beginning to 1st line
C0	Force cursor to beginning to 2nd line
90	Force cursor to beginning to 3rd line
D0	Force cursor to beginning to 4th line
38	2 lines and 5×7 matrix (8-bit mode)
28	2 lines and 5×7 matrix (4-bit mode)
n	Next line
t	Tab
r	enter

Program 1: To display "Hai" in LCD 
code:

#include<reg51.h>
sbit rs=P2^0;
sbit en=P2^1;
void cmd(int);
void data1(char);
void lcd();
void delay();
void display(char *);
void main()
{
 lcd();
 display("Hai");
}
void lcd()
{
 cmd(0x38);
 cmd(0x0e);
 cmd(0x01);
 cmd(0x06);
 cmd(0x80);
}
void cmd(int a)
{
 P3=a;
 rs=0;
 en=1;
 delay();
 en=0;
}
void data1(char x)
{
 P3=x;
 rs=1;
 en=1;
 delay();
 en=0;
}
void display(char *s)
{
 while(*s!='\0')
 {
  data1(*s);
  s++;
 }
}
void delay()
{
 int i,j;
 for(i=0;i<100;i++)
 for(j=0;j<100;j++);
}

simulation:

Download code Here: