8051 micro controller with key pad interfacing

1. EN equ P2.0
RS equ P2.1
RW equ P2.2
mov A,#38H ; Setting Up the LCD
lcall command
mov A,#0EH ; Display On
lcall command
mov A,#06H ; Entry Mode
lcall command
mov a,#82H
lcall command
lcall disp ; Function Disp Called
mov a,#02H ; Setting DDRAM Address to Home position
lcall command
lcall delay1
; Displays BOTSKOOL SHOBHIT ON FIRST LINE OF LCD
mov a,#'B'
lcall datw
NOP
mov a,#'0'
lcall datw
NOP
mov a,#'T'
lcall datw
mov a,#'S'
lcall datw
NOP
mov a,#'K'
lcall datw
NOP
mov a,#'0'
lcall datw
NOP
mov a,#'0'
lcall datw
NOP
mov a,#'L'
lcall datw
NOP
mov a,#' '
lcall datw
NOP
mov a,#'S'
lcall datw
NOP
mov a,#'H'
lcall datw
NOP
mov a,#'O'
lcall datw
NOP
mov a,#'B'
lcall datw
NOP
mov a,#'H'
lcall datw
NOP
mov a,#'I'

2. lcall datw
NOP
mov a,#'T'
lcall datw
MOV A,#255 ; Moving Value 255 to PORT 3
MOV P3,A
; Keypad Scan Begins
sd:
lcall delay1
lcall key1
lcall delay
lcall key2
lcall delay
lcall key3
lcall delay
lcall key4
lcall delay
lcall sd
; Function to Send Commands to LCD
command:
clr RW
clr RS
setB EN
MOV P1,A
lcall delay
clr EN
RET
; Function to Clear the DDRAM Content
clear:
mov A,#01H
lcall command
lcall delay
mov A,#02H ; Set The DDRAM Address to Home Position
lcall command
lcall delay
RET
; Function to Display Data on LCD Screen
datw:
SETB RS
clr RW
SETB EN
MOV P1,A
lcall delay
clr EN
RET
;Function to Display The Key Pressed
datw1:
lcall delay1
lcall disp
lcall delay1
MOV A,R7
lcall datw
RET

3. ; Generating Small Delay
delay:
mov r0,#255
loop: DJNZ r0,loop;
RET
; Generating a Bigger Delay
delay1:
mov r1,#255
loop1: mov r3,#120
loop2: djnz r3,loop2
djnz r1,loop1
RET
; Checking for Key Press on The First Column of 4x4 Matrix
KEY1:
MOV A,r5
MOV r6,A
clr p3.4
MOV A,p3
ANL A,#0FH
MOV r2,A
cjne r2,#14,n1
MOV r7,#'1'
lcall datw1
lcall delay1
n1: cjne r2,#13,n2
mov r7,#'5'
lcall datw1
lcall delay1
n2: cjne r2,#11,n3
mov r7,#'9'
lcall datw1
lcall delay1
n3: cjne r2,#7,n4
mov r7,#'D'
lcall datw1
lcall delay1
n4: lcall delay1
SETB P3.4
RET
; Checking for Key Press on the Second Column of 4x4 Matrix
KEY2:
clr p3.5
MOV A,p3
ANL A,#0FH
MOV r2,A
cjne r2,#14,q1
mov r7,#'2'
lcall datw1
lcall delay1
q1: cjne r2,#13,q2
mov r7,#'6'

4. lcall datw1
lcall delay1
q2: cjne r2,#11,q3
mov r7,#65; A=65
lcall datw1
lcall delay1
q3: cjne r2,#7,q4
mov r7,#'E'
lcall datw1
lcall delay1
q4: lcall delay
SETB p3.5
RET
; Checking for Key Press On The Third Column of 4x4 Matrix
KEY3:
clr p3.6
MOV A,p3
ANL A,#0FH
MOV r2,A
cjne r2,#14,w1
mov r7,#'3'
lcall datw1
lcall delay1
w1: cjne r2,#13,w2
mov r7,#'7'
lcall datw1
lcall delay1
w2: cjne r2,#11,w3
mov r7,#'B'
lcall datw1
lcall delay1
w3: cjne r2,#7,w4
mov r7,#'F'
lcall datw1
lcall delay1
w4: lcall delay1
SETB p3.6
RET
; Checking for Key Press on the Fourth Column of 4x4 Matrix
KEY4:
clr p3.7
MOV A,p3
ANL A,#0FH
MOV r2,A
cjne r2,#14,e1
mov r7,#'4'
lcall datw1
lcall delay1
e1: cjne r2,#13,e2
mov r7,#'8'
lcall datw1
lcall delay1
e2: cjne r2,#11,e3
mov r7,#'C'
lcall datw1

5. lcall delay1
e3: cjne r2,#7,e4
mov r7,#'G'
lcall datw1
lcall delay1
e4: lcall delay1
SETB p3.7
RET
disp:
mov a,#0c0H ; Setting DDRAM Address on Second Line
lcall command
; Clearing the Previous Key Pressed Information from Screen
mov a,#' '
lcall datw
mov a,#' '
lcall datw
mov a,#' '
lcall datw
mov a,#' '
lcall datw
mov a,#' '
lcall datw
mov a,#' '
lcall datw
mov a,#0c0H ; Setting DDRAM Address on Second Line To Display “Key Pressed”
lcall command
; Display "KEY" and Pressed Information
mov a,#' '
lcall datw
mov a,#'K'
lcall datw
mov a,#'E'
lcall datw
mov a,#'Y'
lcall datw
mov a,#' '
lcall datw
RET
END
The code was written when I was learning assembly language myself and therefore the code is not
optimized, but it is easy to understand if someone is willing to check the instruction set.
People who want to optimize the code may wish to look into the DPTR Register and Addressing Modes
Theory.
A View of the Simulation