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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Wed Sep 20 2017, 12:36 AM
Ted
In a missing pulse detector using a 555 timer connected as a monostable vibrator with a PNP transistor,how does the positve input pulse turn on the PNP transistor?
Sun Sep 03 2017, 02:29 PM
martymarty
How do I connect an <NOKIA 1100 LCD > to an atmega328P ?
poojab51296
Sun Aug 20 2017, 10:23 AM
i am intending to interface sd card with STM32F4 and want to write a file in sd card using SPI protocol but using HAL only. Can anyone help me PLEASE!!!!
poojab51296
Sun Aug 20 2017, 10:22 AM
hello
rawat742
Fri Aug 18 2017, 11:37 AM
hi @ angel patel i will attach a file i hope it will be helpfull for you
ExperimenterUK
Mon Aug 14 2017, 09:57 PM
@ angel patel... just log in and post your problem
Mon Aug 14 2017, 01:45 PM
angel patel
hey any one help to make the led scrolling display
desuza6
Sat Jul 29 2017, 07:09 AM
I see the code for step motor h l 298 to rotate 45 degree, but all delay time, if I want to input sensor to h the pulses to stepmotor
rammichael
Thu Jul 27 2017, 12:05 PM
okay fine
ExperimenterUK
Wed Jul 26 2017, 07:51 PM
Please post questions in the forum, the chat box is for chat

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Posted By ExperimenterUK
Thu Sep 21 2017, 01:33 AM
You could start with this tutorialhttp://www.8051p...
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Posted By komal_97
Wed Sep 20 2017, 12:25 PM
hey, i want to interface 3 dc motors with the micr...
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Mon Sep 11 2017, 12:07 AM
The hardware for connecting to a PC or a modem is...
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Posted By Suseethra
Sat Sep 09 2017, 09:43 AM
Hi,we are doing the same project(LED scrolling dis...
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Mon Aug 28 2017, 07:21 PM
First you have to decide which version of the 8051...
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Sat Aug 26 2017, 12:36 PM
Dear Sir, I want to purchase progra...
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Fri Aug 25 2017, 08:22 PM
Debuggers and programmers are different things.Whi...
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Thu Aug 24 2017, 04:30 PM
Dear Sir, if I am not purchase debugger then how ...
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Thu Aug 24 2017, 06:27 AM
I am using STM32 cube MX and Atollic truestudio so...
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Wed Aug 23 2017, 01:30 PM
It will be easier to help if you can post the comp...