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LCD Commands

The commands for HD44780 chip are shown in the table below. Scroll down to see the commands in binary, and more info on the entry mode set command.

INSTRUCTION
Decimal
Hexadecimal
Function set (8-bit interface, 2 lines, 5*7 Pixels)
56
38
Function set (8-bit interface, 1 line, 5*7 Pixels)
48
30
Function set (4-bit interface, 2 lines, 5*7 Pixels)
40
28
Function set (4-bit interface, 1 line, 5*7 Pixels)
32
20
Entry mode set
Scroll display one character right (all lines)
28
1E
Scroll display one character left (all lines)
24
18
Home (move cursor to top/left character position)
2
2
Move cursor one character left
16
10
Move cursor one character right
20
14
Turn on visible underline cursor
14
0E
Turn on visible blinking-block cursor
15
0F
Make cursor invisible
12
0C
Blank the display (without clearing)
8
08
Restore the display (with cursor hidden)
12
0C
Clear Screen
1
01
Set cursor position (DDRAM address)
128 + addr
80+ addr
Set pointer in character-generator RAM (CG RAM address)
64 + addr
40+ addr
Read DDRAM/CGRAM & Check Busy Flag

Entry mode set command

This command sets cursor move direction and display shift ON/OFF. There are 4 possible function set commands;04, 05, 06, and 07. This command changes the direction the cursor moves by setting the address counter to increment or decrement. This command is very important. If you do not understand it you may not see anything or what you actually wanted to see on LCD screen. I have created 4 animated gifs to demonstrate what the function set command is all about.

When my friend Hakan Dereli wanted to learn about LC displays I gave him an LC display and the 4*4 keyboard that I used with my Z80 system.The keyboard is based on a 74C922 chip and my circuit to convert the 4 bit data output of the 74C922 to 8 bit data.It also has 3 other buttons on it.This makes it great to experiment with LCDs by entering commands/data manually. Hakan tested all possible commands by sending all the numbers between 00h and FFh to the LCD to see if there is an undocumented feature and see how all commands work. He did not find anything undocumented, but he noted how LCD behaves after each function set command.

Below are the gifs to demonstrate those commands. To demonstrate the effect of each function set command it is assumed that the LCDs below are 2*16 LC Displays with DD RAM address set to 8 and underline cursor ON. Note that when the address counter is set to DECREMENT, strings sent to the LCD will be printed in reverse order. The same thing applies to the CG RAM, as well.


Entry mode set command 04h

Entry mode set command 04h

Decrement Address Counter

Display Shift :OFF

String:Dereli


Entry mode set command 05h

Entry mode set command 05h

Display Shift :ON

Decrement Address Counter

String :Hakan


Entry mode set command 06h

Entry mode set command 06h

Display Shift :OFF

Increment Address Counter

String:Dereli

 


Entry mode set command 07h

Entry mode set command 07h

Display Shift :ON

Increment Address Counter

String:Hakan


Checking the Busy Flag

To check the state of the busy flag and read the address counter

  1. Set R/W Pin of the LCD HIGH(read from the LCD)
  2. Select the instruction register by setting RS pin LOW
  3. Enable the LCD by Setting the enable pin HIGH
  4. The most significant bit of the LCD data bus is the state of the busy flag(1=Busy,0=ready to accept instructions/data).The other bits hold the current value of the address counter.

*This is a 1-micro-second instruction.


Complete command reference:

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