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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Sun May 20 2018, 01:46 PM
justinb
how to write and execute a program that read the keypad button and display the number on 7 segment on intel8051 at89s52 in assembly language?
Thu May 17 2018, 10:21 AM
HAMZA TAJ
sir iwant to ask about controller of three phase supply by using back to back thyristor instead of triac....will u give me some guideline?
Sat Apr 28 2018, 04:39 PM
ashutosh jain
IR Remote Switch using TV remote (RC5 Protocol) is not working properly. opp1 & opp2 is in problem.plz help
ExperimenterUK
Fri Apr 27 2018, 11:54 PM
@kaiserslautern Post in forum
Wed Apr 25 2018, 10:54 AM
kaiserslautern
Hello everyone, using software uart is a very good idea for a second serial port. Thank you so much. I would kindly like to know how to connect this port to the PC?
ExperimenterUK
Sat Apr 21 2018, 11:35 PM
This is a community site. Feel free to help anyone needing advice
hareeshchamiyar
Thu Mar 29 2018, 02:32 PM
please help me for the configuration bits for dspic30f2010
hareeshchamiyar
Thu Mar 29 2018, 02:30 PM
can any one using dspic30f2010.
Thu Mar 29 2018, 09:48 AM
Neena
can anybody give solar tracking in 8051 using proteus and keil to mail [email protected]
ExperimenterUK
Mon Mar 19 2018, 11:18 PM
sorry bedo.. maybe next time

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bdmehta
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ExperimenterUK Avatar
Posted By ExperimenterUK
Tue Jul 17 2018, 08:31 PM
Thank you.I'm happy it worked out for you.
LAMBO Avatar
Posted By LAMBO
Tue Jul 17 2018, 09:52 AM
hi sir sorry for the late reply thank u sir for he...
ExperimenterUK Avatar
Posted By ExperimenterUK
Thu Jul 12 2018, 08:27 PM
I'm glad we got there in the end :)>whats differen...
LAMBO Avatar
Posted By LAMBO
Thu Jul 12 2018, 06:51 AM
hi sir as u mentioned above to change crystal and ...
ExperimenterUK Avatar
Posted By ExperimenterUK
Tue Jul 10 2018, 07:20 PM
I assume you meant a AT89S52.It seems to me that...
LAMBO Avatar
Posted By LAMBO
Tue Jul 10 2018, 06:06 AM
hi sir i have checked now much of the distortion ...
ExperimenterUK Avatar
Posted By ExperimenterUK
Mon Jul 09 2018, 06:55 PM
Okay that is very interesting.I have attached two ...
LAMBO Avatar
Posted By LAMBO
Mon Jul 09 2018, 08:14 AM
hi sir as u mentioned above program i have tried ...
ExperimenterUK Avatar
Posted By ExperimenterUK
Fri Jul 06 2018, 11:58 PM
Okay..That motor creates a lot of sparks which mig...
LAMBO Avatar
Posted By LAMBO
Fri Jul 06 2018, 01:33 PM
hi sir as u told >Try the original code againi hav...