8051 Microcontroller Lab Manual Lab 07

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Microprocessor & Microcontroller Lab Lab 07: LCD Interfacing

DEE, Faculty of Engineering & Technology, International Islamic University, Islamabad Page 22

Lab 07: LCD Interfacing

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 candisplay 16 characters in a line and there are 2 lines. So maximum 32 characters can be displayedon the 16x2 LCD at a time.Each character is displayed in a 5x7 pixel matrix. There are two registers in an LCD:

1) Data Register:

Data register contains the character to be displayed on the LCD. Data is the ASCII value of

the character to be displayed

2) Command / Instruction Register:

Stores the command / instructions given to the LCD. A command or instruction performsthe 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 aregiven in the Table 2.

Table 2: Pin Description of 16x2 LCD

PIN SYMBOL I/O DESCRIPTION

1 Vss - Power supply (GND)2 Vcc - Power supply (+5V)

3 Vdd - Contrast Adjustment

4 RS I0 = Select command register

1 = Select data register

5 R/W I0 = Write to LCD

1 = Read from LCD

6 E IA high to low pulse (minimum 450ns wide) is given when data issent to data pins

7 DB0 I/O Data bit line 0 (LSB)

8 DB1 I/O Data bit line 1

9 DB2 I/O Data bit line 210 DB3 I/O Data bit line 3




14 DB7 I/O Data bit line 7 (MSB)

15 LED+ - Backlight Vcc +5V

16 LED- - Backlight GND 0V


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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 writesomething 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 datapins 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 displayed 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 flagshould be checked.

Table 2: Command list of 16x2 LCD

S No. Command Description Command

1 Function Set: 8-bit, 1 Line, 5x7 Dots 0x30




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 Programming:

//ThisprogramdisplaysthealphabetfromAtoZontwolinesofLCD#includesbitRS=P1^0; //RegisterSelectPinonP1^0sbitRW=P1^1; //ReadorWriteSelectPinonP1^1sbitE=P1^2; //EnableSelectPinonP1^2sbitBF=P2^7; //BusyFlagonMSBofDataPortchardata1;


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intready() //ForcheckingthattheLCDisreadyornot?{

charch;for(ch=0;ch


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delay(50);LCD_Initialize();for(data1='A';data1

8051 Microcontroller Lab Manual Lab 07

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