Introduction to 4-bit Mode

Till now whatever we discussed in the previous part of ths LCD tutorial, we were dealing with 8-bit mode. Now we are going to learn how to use LCD in 4-bit mode. There are many reasons why sometime we prefer to use LCD in 4-bit mode instead of 8-bit. One basic reason is lesser number of pins are needed to interface LCD.

In 4-bit mode the data is sent in nibbles, first we send the higher nibble and then the lower nibble. To enable the 4-bit mode of LCD, we need to follow special sequence of initialization that tells the LCD controller that user has selected 4-bit mode of operation. We call this special sequence as resetting the LCD. Following is the reset sequence of LCD.
  1. Wait for abour 20mS
  2. Send the first init value (0x30)
  3. Wait for about 10mS
  4. Send second init value (0x30)
  5. Wait for about 1mS
  6. Send third init value (0x30)
  7. Wait for 1mS
  8. Select bus width (0x30 - for 8-bit and 0x20 for 4-bit)
  9. Wait for 1mS

The busy flag will only be valid after the above reset sequence. Usually we do not use busy flag in 4-bit mode as we have to write code for reading two nibbles from the LCD. Instead we simply put a certain ammount of delay usually 300 to 600uS. This delay might vary depending on the LCD you are using, as you might have a different crystal frequency on which LCD controller is running. So it actually depends on the LCD module you are using. So if you feel any problem running the LCD, simply try to increase the delay. This usually works. For me about 400uS works perfect.

LCD connections in 4-bit Mode




Above is the connection diagram of LCD in 4-bit mode, where we only need 6 pins to interface an LCD. D4-D7 are the data pins connection and Enable and Register select are for LCD control pins. We are not using Read/Write (RW) Pin of the LCD, as we are only writing on the LCD so we have made it grounded permanently. If you want to use it.. then you may connect it on your controller but that will only increase another pin and does not make any big difference. Potentiometer RV1 is used to control the LCD contrast. The unwanted data pins of LCD i.e. D0-D3 are connected to ground.

LCD connections in 4-bit Mode

We will now look into the common steps to send data/command to LCD when working in 4-bit mode. As i already explained in 4-bit mode data is sent nibble by nibble, first we send higher nibble and then lower nibble. This means in both command and data sending function we need to saperate the higher 4-bits and lower 4-bits.


The common steps are:
  1. Mask lower 4-bits
  2. Send to the LCD port
  3. Send enable signal
  4. Mask higher 4-bits
  5. Send to LCD port
  6. Send enable signal

We are done with the theory part now, In the next section we will take a look at the programming microcontroller to control LCD in 4-bit mode.

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pravin_35 Avatar
Posted By pravin_35
Thu Jul 31 2014, 01:49 AM
attach is the code for lcd may be need a little ch...
majoka Avatar
Posted By majoka
Wed Jul 30 2014, 02:45 PM
@ sermeteraythank you for sharing your experience ...
majoka Avatar
Posted By majoka
Wed Jul 30 2014, 02:38 PM
@ Peter_ParkerHC06 by default baud rate is 9600try...
majoka Avatar
Posted By majoka
Wed Jul 30 2014, 02:25 PM
attach is the code for lcd may be need a little ch...
majoka Avatar
Posted By majoka
Wed Jul 30 2014, 02:21 PM
@ pravin_35both compilers are almost sameif you ha...
pravin_35 Avatar
Posted By pravin_35
Wed Jul 30 2014, 07:38 AM
http://extremeelectronics.co.in/pic16f877a-tutoria...
NexusRevZ Avatar
Posted By NexusRevZ
Wed Jul 30 2014, 02:31 AM
Ok, I have edited the code, it's updated above wit...
NexusRevZ Avatar
Posted By NexusRevZ
Wed Jul 30 2014, 02:10 AM
Oh tahnk you so much for the reply. I will do imme...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed Jul 30 2014, 01:56 AM
You cannot move and read data from EEPROM immediat...
pravin_35 Avatar
Posted By pravin_35
Wed Jul 30 2014, 12:39 AM
Remove all power connections to the circuit at the...

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NexusRevZ
Tue Jul 29 2014, 09:32 PM
Anyone good in Asm lang?
ajay_bhargav
Mon Jul 28 2014, 12:34 AM
@ Anshu Raj sorry we do not take such requests.
Sun Jul 27 2014, 12:23 AM
Anshu Raj
sir plz send the automatic collage alram bells in 2 hrs bells ring. For microcontroller programme plz sir
ajay_bhargav
Thu Jul 24 2014, 01:06 AM
@R.ABHISHEK where? I dont see it. is it in forum?
Wed Jul 23 2014, 05:49 AM
R.ABHISHEK
sir,pls message on microcontroller 8051 assambly language new program
Wed Jul 23 2014, 05:47 AM
R.ABHISHEK
sir,pls message on 8051 microcontroller assambly language program new quastions
ajay_bhargav
Tue Jul 22 2014, 09:18 AM
@Pragya Android application is taken from google play. Only Author has its source with him. Application is only used in this project.
Tue Jul 22 2014, 04:58 AM
Pragya
plz send me 8051 code and android code for android based device controller via Bluetooth .Here in this project I am using Hc-06 Bluetooth module
Thu Jul 10 2014, 09:57 AM
Caleb
plz someone mail me the source code for that project
Thu Jul 10 2014, 09:57 AM
Caleb
http://www.8051projects.net/download-d188-control-your-pc-tv-remote.html

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ismaelfogaca
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