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.

Share it! Like it!

Conversation

Thu May 25 2017, 05:25 AM
Monir Hossain
Can i change the 7-Segment are common pin ? And how to?
Mon May 08 2017, 12:45 PM
ivan muvunyi
please can you send me wiring diagram for automatic control of 3 phase induction motor for production of maize flour
Wed May 03 2017, 08:39 PM
imran qureshi
hello friend
Sun Apr 30 2017, 05:49 AM
Lijin G Varghese
Can u send me the circuit diagram for Program to interface GSM Module with 8051 microcontroller (AT89C51) using PC and LCD
Fri Apr 28 2017, 03:47 PM
SANDEEP T S
I need pcb wizard 3.5 version kindly send valid link of yours
ExperimenterUK
Mon Apr 17 2017, 11:56 PM
Sorry..We had a problem with registration.Confirmation emails were not sent.Please re-register
Thu Apr 13 2017, 07:29 PM
Piyush Aughad
I want circuit & program for radar detection using Microcontroller 8051
Tue Apr 11 2017, 03:27 AM
Shabbir Ahmed
Hi Ajay ....hope you and your family all will be fine are you working on andriod aplications if yes then plz reply me
Sun Apr 09 2017, 06:33 PM
ATHULYA NAIR
Dear Sir, I need to know what are the complexity for programming in 8051 Microcontroller for three phase inverter?
Sun Apr 09 2017, 06:32 PM
ATHULYA NAIR
Dear Sir,

Downloads

Comments

Gaurav9527
Tue May 23 2017, 10:24 AM
rapushh
Tue May 23 2017, 10:22 AM
lubnakhan
Sat May 20 2017, 10:23 AM
Utsavi
Wed May 17 2017, 10:35 AM
Samimash
Tue May 16 2017, 01:15 PM
gangusa
Mon May 15 2017, 04:34 AM
raghuzala
Sun May 14 2017, 02:32 PM
Prakashlimbachiya
Sat May 13 2017, 07:34 AM

Online

Guests: 52, Members: 0 ...

most ever online: 182184
(Members: , Guests: 182184) on 06 Aug 2010: 05:37 AM

Members: 37829
Newest member: Gaurav9527
Forum Activity
yogesh puri Avatar
Posted By yogesh puri
Thu May 25 2017, 10:33 PM
dear sirif i simulate the above program in keil it...
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed May 24 2017, 09:42 PM
If you run the display in 4 bit mode and share pin...
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed May 24 2017, 09:27 PM
Please post your code and Proteus file.
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed May 24 2017, 09:23 PM
i am unable to simulate following code in protous...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed May 24 2017, 05:01 AM
Duplicate post of http://www.8051projects.net/t651...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed May 24 2017, 05:00 AM
All I can say looking at the post is "insufficient...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed May 24 2017, 04:58 AM
(the 3 motorsteppers need to move independently, b...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed May 24 2017, 04:55 AM
I am never sure with Proteus keypad. They always h...
yogesh puri Avatar
Posted By yogesh puri
Tue May 23 2017, 10:36 PM
i am unable to simulate following code in protous....
yogesh puri Avatar
Posted By yogesh puri
Tue May 23 2017, 10:34 PM
i am unable to simulate following code in protous...