8051 Microcontroller Lab Manual Lab 07

Microprocessor & Microcontroller Lab

Lab 07: LCD Interfacing

Lab 07: 07: L CD Interfaci Interfaci ng Objective: 1. To interface the LCD with 8051 in 8 bit mode 2. Code 8051 for display of alphabets on LCD

Introduction: The LCD available on the 8051 development board is 2x16 LCD which means that this LCD can display 16 characters in a line and there are 2 lines. So maximum 32 characters can be displayed on the 16x2 LCD at a time. Each character is displayed in a 5x7 pixel matrix. There are two registers in an LCD: 1) Data Regist er:

Data register contains the character to be displayed on the LCD. Data is the ASCII value of the character to be displayed 2) Command / Instru cti on Register:

Stores the command / instructions given to the LCD. A command or instruction performs the predefined task for the LCD. Some of the predefined tasks are clearing the screen, Moving / setting cursor, scrolling the display etc. Some of the commands / instructions are given in the Table 2. Table 2: Pin Pin Descri ption of 16x2 LCD

PIN

SYMBOL

I/O

1 2 3

Vss Vcc Vdd

-

4

RS

I

5

R/W

I

6

E

I

7 8 9 10 11 12 13 14 15

DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7 LED+

I/O I/O I/O I/O I/O I/O I/O I/O -

16

LED-

-

DESCRIPTION DESCRI PTION Power supply (GND) Power supply (+5V) Contrast Adjustment 0 = Select command register 1 = Select data register 0 = Write to LCD 1 = Read from LCD A high to low pulse (minimum 450ns wide) is given when data is sent to data pins Data bit line 0 (LSB) Data bit line 1 Data bit line 2 Data bit line 3 Data bit line 4 Data bit line 5 Data bit line 6 Data bit line 7 (MSB) Backlight Vcc

+5V

Backlight GND 0V

DEE, Faculty of Engineering & Technology, International Islamic University, Islamabad

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Pin No. 4, RS:

Register Select (RS) Pin of LCD is used to select between Command Register and Data Register. If RS is set, Data Register is selected and if RS is zero, Command Register is selected. Pin No. 5, R/W: Read / Write (R/W) Pin of LCD is used to select whether to read from LCD or write something on the LCD. IF R/W pin is set, Read operation is performed. IF R/W is zero, a command / data can be written on the LCD. Pin No. 6, E: Enable (E) Pin of LCD is used to enable the LCD. When this bit goes from low to high, write operation is performed.

To send data on the LCD, data is first written to the data pins with R/W = 0 (to specify the write operation) and RS = 1 (to select the data register). A high to low pulse is given at E pin when data is sent. Each write operation is performed on the positive edge of the Enable signal. To send a command on the LCD, a particular command is first specified to the data pins with R/W = 0 (to specify the write operation) and RS = 0 (to select the command register). A high to low pulse is given at E pin when data is sent. Pin No. 7-14, D0-D7: There are the data bits. An ASCII equivalent of the character to be d isplayed or a command required to be executed by the LCD is sent on these 8-data bits. Data pin8 (D7) of the LCD is busy flag and is read when R/W = 1 & RS = 0. When busy flag=1, it means that LCD is not ready to accept data since it is busy with the internal operations. Therefore before passing any data to LCD, its command register should be read and busy flag should be checked. Table 2: Command list of 16x2 LCD

S No.

Command Descrip tion

Command

1

Function Set: 8-bit, 1 Line, 5x7 Dots

0x30

2


0x38

3


0x20

4


0x28

5

Display off Cursor off (clearing display without clearing DDRAM content)

0x08

6

Display on Cursor on

0x0E

7

Display on Cursor off

0x0C

8

Display on Cursor blinking

0x0F

9

Shift entire display left

0x18

10

Shift entire display right

0x1C


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11

Move cursor left by one character

0x10

12

Move cursor right by one character

0x14

13

Clear Display (also clear DDRAM content)

0x01

14

Return Home

0x02

15

During write operation only shift cursor left (decrement cursor)

0x04

16

During write operation only shift cursor right (increment cursor)

0x06

17

Force the cursor at first line, position zero

0x80

18

Force the cursor at second line, position zero

0xC0

Fig 1: 8051 Development Board - Layout of LCD Interface and 8051 Input Output Ports

C Code for LCD Programmin g: //This program displays the alphabet from A to Z on two lines of LCD #include sbit sbit sbit sbit char

RS=P1^0; RW=P1^1; E=P1^2; BF=P2^7; data1;

//Register Select Pin on P1^0 //Read or Write Select Pin on P1^1 //Enable Select Pin on P1^2 //Busy Flag on MSB of Data Port


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int ready() //For checking that the LCD is ready or not? { char ch; for(ch = 0; ch < 100; ch++); return 1; } //Ready Function Ends void delay( unsigned int z) //For delay (Starts) { int x, y; for(x = 0; x < z; x++) for(y = 0; y <= 1000; y++); } //Delay Function Ends int LCD_Run_Command(unsigned char COMMAND) { if(ready()) { P2 = COMMAND; RS = 0; delay(1); RW = 0; delay(1); E = 0; delay(1); E = 1; delay(1); } return 1; } void LCD_Show(unsigned char CHARACTER) { if(ready()) //if LCD internal controller is not busy { P2 = CHARACTER; RS = 1; delay(1); RW = 0; delay(1); E = 0; delay(1); E = 1; delay(1); } } void LCD_Initialize() { LCD_Run_Command(0x38); LCD_Run_Command(0x0E); LCD_Run_Command(0x01); LCD_Run_Command(0x06);

// // // // //

8 data lines, two lines, Font 5x7. Display=ON, Curson=ON, Cursor Blonking=ON Clear display and return cursor to the home position During read/write operation only cursor (not text) should move right

} void main(void) { while(1) {


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Microprocessor & Microcontroller Lab delay(50); LCD_Initialize();


for(data1 = 'A'; data1 <= 'N'; data1++) LCD_Show(data1); //Display characters A to N on LCD Line 1

LCD_Run_Command(0xC0); // Cursor at Line 2, Position 0 for(data1 = 'O'; data1 <= 'Z'; data1++) LCD_Show(data1); //Display character O to Z on LCD Line 2

delay(50); } }

Simulation:

Lab Task: At the center of first line of LCD, show “ GROUP No. XX” where XX is your group number. At the center of second line, display the first name of your group leader.


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8051 Microcontroller Lab Manual Lab 07

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