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# LCD Interfacing with 8051

• The LED 7-segment display consumes more power which makes it unsuitable for battery operated devices. On the contrary, LCD display consumes less power which makes it suitable for battery operated devices. Example- calculator, mobile.

• LCD is more flexible in terms of size, shape and has ability to display numbers, characters, words, letter and graphics with simple interface.

• LED displays require refreshing circuit which is done by microcontroller to keep the display. Whereas LCD has its own refreshing circuit which reduces the burden of microcontroller.

• The LCD displays are classified and designated depending upon no. of lines and no. of characters to be displayed on each line such as:

• 1. 1x16 character LCD
2. 2x16 character LCD
3. 2x20 character LCD
4. 2x40 character LCD
5. 4x40 character LCD etc.
• The interfacing of 2x20 character LCD with Microcontroller 8051 is shown n figure.

• The following are the role of different pins of LCD:-

• 1. VCC,VSS and VEE:
VCC and VSS provide the +5V and Ground to the LCD and VEE is used for contrast adjustment of LCD.

2. RS(Register Select):
There are two important registers inside LCD viz.
i. Instruction command code register
ii.Data register

The RS control signal is used to select one of the register of LCD. When RS=’1’ then data register is selected and when RS='0' then instruction command code register is selected.

It allows user to read/write command or data to LCD. When this pin is at logic’1’, then it performs write command or data and when it is at logic'1' then it reads status information from LCD.

4. E(Enable):

It is used as latch. When a high to low signal is applied to this pin and then the latch get enabled and the data/command received is stored in the LCD.

5. D0-D7:

It is an 8-bit data bus which is used to send data/command to LCD to displaying various numbers/characters etc.

• The following are the command codes for LCD which can be sent to instruction register to perform a particular operation.

• ## Program

 LABEL OPCODE OPERAND COMMENT ORG 0000H MOV A,#38H ACALL COMMAND ACALL DELAY MOV A,#0EH ACALL COMMAND ACALL DELAY MOV A,#01H ACALL COMMAND ACALL DELAY MOV A,#06H ACALL COMMAND ACALL DELAY MOV A,#84H ACALL COMMAND ACALL DELAY MOV A,#’N’ ACALL DISPLAY ACALL DELAY MOV A,#’O’ ACALL DISPLAY ACALL DELAY AGAIN: SJMP AGAIN COMMAND: MOV P1,A CLR P2.0 CLR P2.1 SETB P2.2 ACALL DELAY CLR P2.2 RET DISPLAY: MOV P1,A SETB P2.0 CLR P2.1 SETB P2.2 ACALL DELAY CLR P2.2 RET DELAY: MOV R3,#50 L2: MOV R4,#255 L1: DJNZ R4,L1 DJNZ R3,L2 RET END

## Interfacing Diagram

CACKLE comment system