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

ExperimenterUK
Thu Nov 20 2014, 06:00 PM
@Mehboob.. I don't think you can do that.
Sat Nov 15 2014, 06:41 AM
Mehboob
Pls can you send me code in c of PWM generation using UART/serial port in 8051.
Fri Nov 14 2014, 02:51 PM
mohammad aqil
NEED A BOOK ON MICROPROCESSOR AND INTERFACING BY D.V.HALL. RIGHT NOW, I SHALL BE VERY THANK FULL TO U....
Thu Nov 13 2014, 02:15 PM
m
please code hex project avr blood pressure monitor
Thu Nov 13 2014, 05:56 AM
Lambo
hi mate, whats the ajay-bhargav? tell us more pls
ExperimenterUK
Wed Nov 12 2014, 12:56 AM
@tmtm000.. have you been able to join ?
ExperimenterUK
Wed Nov 12 2014, 12:54 AM
@Alice..become a member,then send a PM to ajay_bhargav the site owner.
Tue Nov 11 2014, 03:58 AM
Abhishek Bansal
Thanks a lot for your informative tutorials!
Mon Nov 10 2014, 09:03 AM
Alice
Hello, This is Alice from a PCB rototype manufacturer. Our company is interested in your website contents, and wonder if we can advertise our company with payment on your website. There are two ways to advertise: first, if we an get a instant quote section on your main site columns; second, whether we can get a advertising section if you have any avaliable one. If any of above ways avaliable, please contact me with your detailed scheme and advertising charge. Thanks. Alice
Sat Nov 08 2014, 11:58 AM
Mohamed_123sd
Signals and Systems, 2nd Edition by Alan V. Oppenheim Alan S.willsky with S.Hamid Nawab?

Downloads

Comments

dpkraju
Wed Nov 26 2014, 02:18 PM
sankalp_s
Tue Nov 25 2014, 05:13 PM
dodul
Mon Nov 24 2014, 10:08 PM
VikiPeter
Tue Nov 18 2014, 09:13 AM
gentlboy
Sun Nov 16 2014, 11:13 PM
philipeastbourne
Wed Nov 12 2014, 05:32 AM
astra91
Mon Nov 10 2014, 08:11 AM
francise
Thu Nov 06 2014, 02:55 AM

Online

Guests: 62, Members: 0 ...

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

Members: 37550
Newest member: dpkraju
Forum Activity
rearthur2003 Avatar
Posted By rearthur2003
Thu Nov 27 2014, 05:23 AM
there are two types of diodes ir rx which is coat...
rearthur2003 Avatar
Posted By rearthur2003
Thu Nov 27 2014, 05:19 AM
First you will need to let us know what IDE you pl...
engr1931 Avatar
Posted By engr1931
Thu Nov 27 2014, 05:18 AM
yes sir! i only know assembly, and still in proces...
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed Nov 26 2014, 06:36 PM
I never tried sending SMS messages at a high rate,...
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed Nov 26 2014, 06:23 PM
connected my modem with Laptop via serial2usb cabl...
dodul Avatar
Posted By dodul
Wed Nov 26 2014, 04:30 PM
Hi,Thanks a lot for your reply. Yes i was referrin...
nomi77 Avatar
Posted By nomi77
Wed Nov 26 2014, 07:30 AM
@ajayAnother option is this if i can do void stor...
nomi77 Avatar
Posted By nomi77
Wed Nov 26 2014, 07:05 AM
@ajayI did same procedureconnected my modem with L...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed Nov 26 2014, 04:47 AM
Are you manually trying to input data via virtual ...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed Nov 26 2014, 04:39 AM
Uart is totally different peripheral. Look at seri...