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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Conversation

Tue Nov 29 2016, 02:49 PM
jaykumar
Dear sir, elevator microprocessor control , the vendor locked the control, pls help me how can we decode the password
Sat Nov 26 2016, 10:24 AM
manikanta B
hello i know about gsm,gps and zigbee but i dont know how to use them while programming. can anyone suggest me how to use them
ExperimenterUK
Sat Nov 19 2016, 07:09 PM
@Protaz.. Really you would be better off asking on one of the many Arduino user sites
Fri Nov 18 2016, 05:39 AM
Protaz
Hi, am new in programing, but I have few skills in electronic. I want to make an automatic timing system for institutions using arduino uno. Any one to assist me how to program the microcontoller?
Tue Nov 15 2016, 04:45 AM
Hemangi patel
hello, i am working on atmega128 board and i want to interface with sd card with using fat32 file system. i am totaly new in this field .so pls anyone can u suggest me some imp links.thanks
Thu Nov 10 2016, 01:40 PM
ajith raj
hi frds i make voice control robot using blutooth module
Wed Oct 26 2016, 08:23 AM
ishalt
is it possible to completly get the robot running from java code
Sun Oct 23 2016, 05:50 PM
mamata thakur
plz send full mini project report for ic 741&ic 555 tester
Wed Oct 19 2016, 03:30 PM
riddhi1296
can you provide an explanation for the inverter 8051 code and how it works
ExperimenterUK
Sat Oct 15 2016, 12:15 AM
@snaya. Create a thread in the 8051 forum for your questions

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Jonathan.kei
Mon Nov 21 2016, 04:30 PM
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Thu Nov 17 2016, 07:44 PM
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Mon Nov 14 2016, 05:54 PM
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Wed Nov 02 2016, 02:03 PM
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Thu Oct 27 2016, 01:54 PM
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Sat Oct 15 2016, 09:40 AM

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