Saturday, 6 December 2014

Write an ALP program for 4x4 matrix keypad

Posted by Madan Posted on 22:11 
ROW0 BIT P3.0
ROW1 BIT P3.1
ROW2 BIT P3.2
ROW3 BIT P3.3

COL0 BIT P3.4
COL1 BIT P3.5
COL2 BIT P3.6
COL3 BIT P3.7

KEYPAD_LUT SEGMENT CODE
RSEG KEYPAD_LUT
KCODE0:	DB 1,2,3,4
KCODE1:	DB 5,6,7,8
KCODE2:	DB 9,+,-,*

INIT_ROWS:
CLR ROW0
CLR ROW1
CLR ROW2
clr row3
RET

INIT_COL:
SETB COL0
SETB COL1
SETB COL2
SETB COL3
RET

COLSCAN:
SETB C
ANL C,COL0
ANL C,COL1
ANL C,COL2
ANL C,COL3
RET

CSEG AT 0
MAIN:
KEYSCAN:
ACALL INIT_COL
ACALL INIT_ROWS
SCAN_COLS:
ACALL COLSCAN
JNC KEYPRESSED
SJMP SCAN_COLS

KEYPRESSED:
CLR ROW0
SETB ROW1
SETB ROW2
SETB ROW3
ACALL COLSCAN
JNC ROW_0

SETB ROW0
CLR ROW1
SETB ROW2
SETB ROW3
ACALL COLSCAN
JNC ROW_1

SETB ROW0
SETB ROW1
CLR ROW2
SETB ROW3
ACALL COLSCAN
JNC ROW_2

SETB ROW0
SETB ROW1
SETB ROW2
SETB ROW3
ACALL COLSCAN
JNC ROW_2


ROW_0:
MOV DPTR,#KCODE0
SJMP COLCHECK


ROW_1:
MOV DPTR,#KCODE1
SJMP COLCHECK


ROW_2:
MOV DPTR,#KCODE2
SJMP COLCHECK

COLCHECK:
MOV R3,#0
JNB COL0,MAPKEY
INC R3
JNB COL1,MAPKEY
INC R3
JNB COL2,MAPKEY

MAPKEY:
MOV A,R3
MOVC A,@A+DPTR
MOV P2,A

IS_KEY_PRESSED:
ACALL COLSCAN
JNC IS_KEY_PRESSED
SJMP MAIN
END

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