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.
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.
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: 40×4 and sizes greater than it has two enable pins E1 and E2.
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.
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.
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