This document discusses interfacing an LCD display to an 8051 microcontroller. It covers the objectives of connecting an LCD to an 8051, deciding which ports to use, important LCD commands, timing considerations, and writing a subroutine to write data to the LCD. Example pseudo-code is provided to initialize the LCD and display text on the two lines by calling subroutines to write commands and data. Additional steps are needed during hardware testing to fully initialize the LCD. The tasks for the lab involve displaying a workstation number and student IDs on the LCD's two lines.

1. INTERFACING LCD DISPLAY USING 8051

2. Objectives of the Lab
 Learning pin configurations of 8051
 Learning important commands for LCD
 Learning subroutines for displaying command and data
 Displaying specific data on LCD.

3. Deciding Pins or Ports to use
Use with
caution
If EA high
*As LCD needs
11 pins, we will
use P2 and P3.

4. LCD
 Keypads are usually used
for displaying messages.
 There are 2 lines and
each line can display 16
characters. That’s why it
is called 16x2 line
display.
 It is widely used in
applications that use
MENU or display values.
 It is a good alternative
for SSDs.

5. Pin Configuration

6. Important Commands
1.
2. on
3.
4.

7. Instructions used in this Lab
 SETB Px.y
 CLR Px.y
 NOP
 See instruction set for the details of above commands.

8. LCD Timing for Read

9. LCD Read Subroutine (BF check)
 LCD read is only needed to check busy flag, to check if LCD is
busy. Busy flag is D7. If it is set, the LCD is busy
1. RS=0
2. R/ 𝑊=1
3. E=0 => E=1
4. Stay here if bf=1.
There is a passive way to send command or data without
checking the BF of LCD. If delay greater than 200 nanoseconds
is between the commands or data for LCD, there is no need for
BF.

10. LCD Timing for Write

11. LCD Write subroutine
 LCD write is used for writing command and/or data to
LCD.
1. Move data in A to port where Data pins of LCD are
connected.
2. RS=0 for command, RS=1 for data.
3. R/ 𝑊=0
4. E=1 => E=0
5. Check BF or give delay.

12. Pin naming and data display
 Instead of calling pins by their ports, we can also give custom
names to pins and use it during code e.g.
rs bit p3.5 => setb rs; this means setb p3.5
rw bit p3.6 and en bit p3.7.
 This is done below ‘org 00h’ and above the rest of the code.
For port, mydata equ P2 (pin 2.0 to D0 and so on…)
 To display character use mov a,#‘X’.
 To display integer, first make it ASCII, add a,30h.
 To display a line, use look-up table.
line1: db “HELLO WORLD”,0
 Soon, we will see the need to append 0 at the end of line.

13. Subroutine for Writing
Command/Data
Label
Clear/Set
RS
Call Delay
setb en
nop
clr en
Move
command/
data to P2
H to L
pulse to
enable
ret

14. Using Lookup Table for display
 The display of character array is simple, the difficult task is to end
that display. For this, we keep a zero at the end of the line and check
if the data is zero.
mov dptr,#line1
again:
mov a,#0
movc a,@a+dptr
inc dptr
jz exit1; jump if accumulator is zero
call data_wrt; subroutine to display single character
jmp again
exit1:
line1: db “Hello World”,0

15. Semi-final Pseudo-Code
 What we have to do to display overall data on LCD is
following
1. Define pin and port names
2. Initialize LCD by sending (38h,0Eh,01h followed by
command write subroutine)
3. Then data of line1 using lookup table (use data write
subroutine)
4. Then data of line2 using lookup table (use data write
subroutine)
5. Command Write Subroutine and Data Write Subroutine
6. Delay Subroutine

16. Final Pseudo-Code
 The above Pseudo code works during software test but during
hardware we need to add some more steps before step 2.
 We need to send 030h, commands 3 times with a delay of 50
milli-seconds to initialize the hardware LCD which during
software is not needed.

17. Proteus Devices needed in this Lab
1. AT89c51
2. 16x2 LCD

18. Lab Tasks
 Display Workstation#XY on line1 and ID numbers on line
2.
 Quiz Next Week of Keypad and Stepper Motor.
 Individual Project Briefing during Experiment.