HD44780 LCD- Character Mode

The HD44780 LCD can be in two modes: Character Mode or Instruction Mode.

The HD44780 has 8 data pins, which is how a user submits data to the LCD. When the LCD is in character mode, the data on the data pins represents the character(s) that the LCD will display. When the LCD is in instruction mode, the data on the data pins represents the instruction(s) that the LCD should execute.

There are many different kinds of characters that can be sent to the LCD, including all the alphanumerical characters, special symbols, and also Japanese characters.

Below is the chart of the characters that the HD44780 LCD can display:

Using this chart, we can display a range of characters on our HD44780 LCD.

How to Set the LCD to Character Mode

The Register Select (RS) pin of a HD44780 LCD is the pin which enables a user to select the instruction mode or the character mode of a LCD. This is pin 4 of the LCD.

How to Wire

Instruction Mode- RS pin set to low (or ground)
Character Mode- RS pin set to high (or Vcc)

So in order to set the RS pin to Character mode, we wire the RS pin to high or Vcc.

This is the full schematic of how to wire up a HD44780 LCD:

How to Switch Between Both Modes

If you just want to set the LCD permanently to Character Mode, you can simply wire the RS pin to Vcc. However, usually, we connect the RS pin (pin 4) so that we can switch between the 2 modes whenever we want.

In this schematic above, the RS pin is wired so that we can switch between Character Mode and Instruction Mode.

Being that both instruction and character modes are used when using a HD44780 LCD, many times we want to go back and forth between these 2 modes. The way to go back and forth between these 2 modes in an easy way is to connect a SPST switch between Vcc and ground. When the switch is open, the LCD is in character mode. When the switch is closed, the LCD is in instruction mode.

This allows us flexibility to go between Instruction and Character Mode of the RS pin.