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

ajay_bhargav
Mon Oct 20 2014, 11:22 AM
@skrishna, please post in forum so we can help you better.
Tue Oct 14 2014, 01:45 PM
skrishna
how do i write an ALP equivalent 7segment display interfacing embedded c program (both 8051 microcontroller)
Sat Oct 11 2014, 06:41 PM
vaidehi
want details of seven segment LED display common cathode ( IC CD 4026)
Fri Oct 03 2014, 12:52 PM
Narsim
Rickey you inspired me a lot ... I am also planing like you ...
ExperimenterUK
Wed Oct 01 2014, 09:33 PM
We're back.. we had a bug, but posting is back to normal
ExperimenterUK
Sat Sep 13 2014, 04:34 PM
jaimin1212,Pimpalkhare Create a thread for your question
jaimin1212
Sat Sep 13 2014, 06:35 AM
i want to make self balancing robot using MPU6050 using atmega8.. please help to get data of gyro and accelerometer from this sensor through atmega8.
Thu Sep 11 2014, 01:00 PM
Sunil Pimpalkhare
Hello sir, I am trying to make Wearfin project https://www.youtube.com/watch?v=iZ6PVBvQf-g so can u help me in teaching how to built the program???
Thu Sep 11 2014, 06:21 AM
hariom panday
plz hlp me in my project
iec.naga
Tue Sep 09 2014, 05:19 AM
spi

Downloads

Comments

pddung93
Sun Oct 19 2014, 01:56 PM
msideal
Thu Oct 16 2014, 08:48 AM
robotgirl
Tue Oct 14 2014, 06:23 PM
BRV64
Mon Oct 13 2014, 05:48 AM
menadjelia
Mon Oct 13 2014, 02:47 AM
kulbhushan
Sun Oct 12 2014, 12:20 PM
HarrySid
Fri Oct 10 2014, 05:15 AM
pphamtuan
Thu Oct 09 2014, 03:58 AM

Online

Guests: 47, Members: 0 ...

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

Members: 37531
Newest member: pddung93
Forum Activity
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Oct 20 2014, 11:19 AM
Use a 8bit shift register with latch control (e.g....
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Oct 20 2014, 11:17 AM
You can use the attach file button to attach the i...
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Oct 20 2014, 11:12 AM
I think you need to first check your code what exa...
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Oct 20 2014, 09:11 AM
I don't have resources to show this but if I get t...
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Oct 20 2014, 09:09 AM
Initialise _data in the header file to some value ...
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Oct 20 2014, 09:07 AM
8051 is slow in doing what? Well I don't think 805...
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Oct 20 2014, 09:00 AM
I also checked in Intel manual however I could not...
msideal Avatar
Posted By msideal
Sun Oct 19 2014, 07:25 PM
Is there anyone who could help me in solving this ...
jona Avatar
Posted By jona
Sun Oct 19 2014, 02:03 AM
Has anyone used this device? I was able to get the...
kirangowle Avatar
Posted By kirangowle
Sat Oct 18 2014, 03:49 PM
Thanks ExperimenterUK