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



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. Instruction Hex Decimal
1Function Set: 8-bit, 1 Line, 5x7 Dots0x3048
2Function Set: 8-bit, 2 Line, 5x7 Dots0x3856
3Function Set: 4-bit, 1 Line, 5x7 Dots0x2032
4Function Set: 4-bit, 2 Line, 5x7 Dots0x2840
5Entry Mode0x066
6Display off Cursor off
(clearing display without clearing DDRAM content)
0x088
7Display on Cursor on0x0E14
8Display on Cursor off0x0C12
9Display on Cursor blinking0x0F15
10Shift entire display left0x1824
11Shift entire display right0x1C30
12Move cursor left by one character0x1016
13Move cursor right by one character0x1420
14Clear Display (also clear DDRAM content)0x011
15Set DDRAM address or coursor position on display0x80 + address*128 + address*
16Set CGRAM address or set pointer to CGRAM location0x40 + address**64 + address**
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.

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ExperimenterUK
Thu Oct 30 2014, 06:02 PM
This is a chat box..create a thread if you need help...but we don't do homework
Tue Oct 28 2014, 07:33 PM
vinni
hi rickey...anyone got the pgm...pls gimme now
Tue Oct 28 2014, 06:35 PM
potla
hi vinni even i need that program. help me if you get it
Tue Oct 28 2014, 03:22 PM
vinni
1. Using a look-up table in Flash ROM and accumulator offset indexed addressing mode, write a program that acts as a timer. The timer should count from 0 to 59 seconds. After reaching 59, it should go back to 0 on the next second and continue to count up. The timer should use the seven-segment display. The look-up table should contain information on how to display the digits 0 – 9 on the seven-segment display
Tue Oct 28 2014, 03:22 PM
vinni
hello Rickey..i need this pgm very urgently
Tue Oct 28 2014, 01:42 AM
Boy Donald
Dear sir, thanks before. i have some project urgent for my school and my project need this digital countdown timer using 7 segmen display. but your project only show ten minutes countdown, i need your help, can you show me more to change the minute or set the time manually. thank you, sorry for disturbing you.
Tue Oct 28 2014, 01:32 AM
Boy Donald
dear sir
Tue Oct 28 2014, 01:19 AM
Boy Donald
Rickey you inspired me a lot but why i can not change the time ( minute
Sun Oct 26 2014, 02:51 AM
sandeep bankar
dear sir I m facing problem about..how to read number of incoming call in gsm 900 a. pls help how to read it in atmel avr microcontroller.
ajay_bhargav
Mon Oct 20 2014, 11:22 AM
@skrishna, please post in forum so we can help you better.

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prash5054
Thu Oct 30 2014, 06:34 AM
Max.otto
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Thu Oct 16 2014, 08:48 AM
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Hi Ajay, I wanted to know can we use transformer ...
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Hello all, before generating i have to give PWM p...
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can u post the updated code for the above problem ...
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Thank you for the feedback.It's good to hear when ...
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