I have an LCD Display HD44780 model and I was reading his datasheets

I saw the it has the functionality to be switched on/off as stated:

Display on/off control: D = 0; Display off // C = 0; Cursor off // B = 0; Blinking off

and by continue reading it states:

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Then he states again:

Display On/Off Control

D: The display is on when D is 1 and off when D is 0. When off, the display data remains in DDRAM.

But I can't reaaly understand what I fisically need to do, can anyone help me out to better understand?

EDIT: For better clarify myfinal goal is to completely (power OFF) the LCD screen, I have some NPN transistors and if this would be the best solution, how about the wiring? do I have only to stop suppying VDO?

2 Answers 2


Assuming that display is initialized in 8-bit mode: to send command such as "Turn display on/off",

  • set RS to LOW first (meaning it is command, not data)
  • set command bits on DB7-DB0 (in your case it could be 0x08 - DB2/DB1/DB0 all LOW to turn off following: display, cursor and blinking)
  • make a pulse on EN pin LOW-HIGH-LOW (take a 40uS delay before further communication)
  • Thanks for the reply, assuming that your answer is correct how would you implement such portion of code?
    – FabioEnne
    Commented Nov 12, 2016 at 19:49
  • There are tons of HD44780 libraries on the Internet. For example LiquidCrystal library for Arduino. Or this one - github.com/aostanin/avr-hd44780
    – Flanker
    Commented Nov 12, 2016 at 20:23

At the end I manage to control the complete poweroff of the screen by connecting the pin 15 of the lcd to the Arduino and with a simple HIGH an LOW set of the arduino pin I was able to power it ON/OFF.

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