Difference between 8-bit and 4-bit mode lcd interfacing mode

Lcd interfaced in 4-bit mode

8x1, 8x2, 8x4, 20x1, 20x2, 20x4, 24x1, 24x2, 24x4, 32x1, 32x2, 40x1, 40x2, 40x4 Lcd Connection with Microcontroller in 8-bit mode.
8x1, 8x2, 8x4, 20x1, 20x2, 20x4, 24x1, 24x2, 24x4, 32x1, 32x2, 40x1, 40x2, 40x4 Lcd Connection with Microcontroller in 4-bit mode.

Lcd interfaced in 8-bit mode

8x1, 8x2, 8x4, 20x1, 20x2, 20x4, 24x1, 24x2, 24x4, 32x1, 32x2, 40x1, 40x2, 40x4 Lcd Connection with Microcontroller.
8x1, 8x2, 8x4, 20x1, 20x2, 20x4, 24x1, 24x2, 24x4, 32x1, 32x2, 40x1, 40x2, 40x4 Lcd Connection with Microcontroller in 8-bit mode.

 Character Pin Functions

DB0-DB7
These are eight bit data pins. We send our data and command to lcd using these lines. Data is directly accepted by the hd44780 lcd controller.

R/W(Read-Write)
This pin selects if we want to read or write some instruction (Data-Command) to lcd. Signals notifies the lcd controller about potential read write operation.
  • If R/W=0 Write operation is selected.
  • If R/W=1 Read operation is selected.

En(Enable)
This pin is a push data present on data lines of lcd. Generally it remains low. But when we want to display data on lcd screen or send lcd settings command we make this pin high for some milli seconds and then back again low. This small push sends the data present on lcd data lines straight  to the HD44780 lcd controller   

Note: 40x4 and sizes greater than it has two enable pins E1 and E2.

RS(Register Select)
This pin selects the lcd register. Each character lcd has two registers Data and Command.
  •  Data Register
          To display data on lcd we have to select data register of lcd. Send data to data register. Now To make this data                 appear on lcd we have to made En(Enable) pin high.
              If RS=1 Data Register is selected.
  •  Command Register
         Before using lcd we have to set some parameters for lcd. Like the font size of data that we want to display on lcd.           Cursor blinking or still settings etc. 
          If RS=0 Command register is selected.

Standard lcd commands and their functions are given below.
8x1, 8x2, 8x4, 20x1, 20x2, 20x4, 24x1, 24x2, 24x4, 32x1, 32x2, 40x1, 40x2, 40x4 Lcd Initializing Commands
8x1, 8x2, 8x4, 20x1, 20x2, 20x4, 24x1, 24x2, 24x4, 32x1, 32x2, 40x1, 40x2, 40x4 Lcd Initializing Commands
V0
V0 sets the contrast for lcd. Attach a variable resistor, potentiometer to this pin and set the exact contrast which makes the text visible to naked eye.

LED+ & LED-
To display the back light of lcd. Supply +5v to LED+ and ground LED-.

Vss & Vdd
Make Vss pin ground and apply +5v to vdd to switch on the lcd.
Some projects that are created by use using 16x2 lcd and various microcontrollers. Visit them below. Each project contains free source code and project circuit diagram.
PLC with Pic microcontroller
Calculator with Arduino, 16x2 lcd and 4x4 keypad
Display your name on lcd using 8051 microcontroller
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