Thursday 3 January 2013

LCD COMMANDS

►Commands and Instruction set

Only the instruction register (IR) and the data register (DR) of the LCD can be controlled by the MCU. Before starting the internal operation of the LCD, control information is temporarily stored into these registers to allow interfacing with various MCUs, which operate at different speeds, or various peripheral control devices. The internal operation of the LCD is determined by signals sent from the MCU. These signals, which include register selection signal (RS), read/write signal (R/W), and the data bus (DB0 to DB7), make up the LCD instructions (Table 3). There are four categories of instructions that:

  • Designate LCD functions, such as display format, data length, etc.
  • Set internal RAM addresses
  • Perform data transfer with internal RAM
  • Perform miscellaneous functions


LCD type HD44780 command and instruction set
Table 3: Command and Instruction set for LCD type HD44780


Although looking at the table you can make your own commands and test them. Below is a breif list of useful commands which are used frequently while working on the LCD.


No. InstructionHexDecimal
1 Function Set: 8-bit, 1 Line, 5x7 Dots 0x3048
2 Function Set: 8-bit, 2 Line, 5x7 Dots 0x3856
3 Function Set: 4-bit, 1 Line, 5x7 Dots 0x2032
4 Function Set: 4-bit, 2 Line, 5x7 Dots 0x2840
5Entry Mode0x066
6 Display off Cursor off
(clearing display without clearing DDRAM content)
0x088
7 Display on Cursor on 0x0E14
8 Display on Cursor off 0x0C12
9 Display on Cursor blinking 0x0F15
10 Shift entire display left 0x1824
12 Shift entire display right 0x1C30
13 Move cursor left by one character 0x10 16
14 Move cursor right by one character 0x1420
15 Clear Display (also clear DDRAM content)0x011
16 Set DDRAM address or coursor position on display 0x80+add* 128+add*
17 Set CGRAM address or set pointer to CGRAM location0x40+add**64+add**
Table 4: Frequently used commands and instructions for LCD

* DDRAM address given in LCD basics section see Figure 2,3,4
** CGRAM address from 0x00 to 0x3F, 0x00 to 0x07 for char1 and so on..

The table above will help you while writing programs for LCD. But after you are done testing with the table 4, i recommend you to use table 3 to get more grip on working with LCD and trying your own commands. In the next section of the tutorial we will see the initialization with some of the coding examples in C as well as assembly.


LCD Tutorial Index
Introduction to LCD Sending command & Data to LCD
Basics of LCD Creating custom characters
LCD Commands LCD in 4-bit Mode - Introduction
Initializing the LCD LCD in 4-bit Mode - Programming
Checking Busy Flag of LCD

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