;           ***********************
;           KEYPAD SCANNING ROUTINE
;           ***********************
;         
;   CONNECTIONS TO HEX KEYPAD:
; 
;              |    |    |    |
;              |    |    |    |
;   P1.7  -----0----1----2----3------
;              |    |    |    |
;   P1.6  -----4----5----6----7------
;              |    |    |    |
;   P1.5  -----8----9----A----B------
;	       |    |    |    |
;   P1.4  -----C----D----E----F------
;	       |    |    |    |
;              |    |    |    |
;            P1.3 P1.2 P1.1 P1.0
;
;----------------------------------------------------------------------------------------;
;DISPLAY IS A SEVEN SEGMENT ATTACHED TO P0                                               ;
;----------------------------------------------------------------------------------------;
;This code is written by Mubashar Yasin(Islamabad,Pakistan).It is freely distributable   ;
;however please distribute it with my name and if you add this code to your website or   ;
;some other publication then mention about me along with this code.I have tested this    ;
;code to work properly even then there is no guarantee or warranty and i cannot be held  ; 
;responsible for any damage or loss due to this code.If you have any querries about this ; 
;code please contact me at:                                                              ;
;                                                                                        ;
;  kool_projects@yahoo.com                                                               ;
;  mubasharpk09@hotmail.com                                                              ;
;                                                                                        ;
;or visit my website:                                                                    ;
;                                                                                        ;
;  http://www.geocities.com/kool_projects                                                ;
;----------------------------------------------------------------------------------------;	
	

	
	ORG 0000H
	LJMP MAIN

;;;;;;;;;;;;;;;;;
KEY_PRESSED:
;;;;;;;;;;;;;;;;;

REPEAT:	;SCANNING THE FIRST ROW
	MOV P1,#07FH
	;CLR P1.7
	JB P1.3,NEXT1
	JNB P1.3,$        ;WAIT FOR KEY RELEASE
	MOV A,#0H
	LJMP EXIT1
NEXT1:  JB P1.2,NEXT2
	JNB P1.2,$
	MOV A,#01H
	LJMP EXIT1
NEXT2:  JB P1.1,NEXT3
	JNB P1.1,$
	MOV A,#02H
	LJMP EXIT1
NEXT3:  JB P1.0,NEXT4
	JNB P1.0,$
	MOV A,#03H
	LJMP EXIT1
	;;;;;;;;;;;;
NEXT4:  ;SCANNING THE SECOND ROW
	MOV P1,#0BFH
	;CLR P1.6
        JB P1.3,NEXT5
	JNB P1.3,$
	MOV A,#04H
	LJMP EXIT1
NEXT5:  JB P1.2,NEXT6
	JNB P1.2,$
	MOV A,#05H
	LJMP EXIT1
NEXT6:  JB P1.1,NEXT7
	JNB P1.1,$
	MOV A,#06H
	LJMP EXIT1
NEXT7:  JB P1.0,NEXT8
	JNB P1.0,$
	MOV A,#07H
	LJMP EXIT1
	;;;;;;;;;;;;
NEXT8:  ;SCANNING THE THIRD ROW
	MOV P1,#0DFH
	;CLR P1.5
	JB P1.3,NEXT9
	JNB P1.3,$
	MOV A,#08H
	LJMP EXIT1
NEXT9:  JB P1.2,NEXT10
	JNB P1.2,$
	MOV A,#09H
	LJMP EXIT1
NEXT10: JB P1.1,NEXT11
	JNB P1.1,$
	MOV A,#0AH
	LJMP EXIT1
NEXT11: JB P1.0,NEXT12
	JNB P1.0,$
	MOV A,#0BH
	LJMP EXIT1
	;;;;;;;;;;;;
NEXT12: ;SCANNING THE FOURTH ROW
	MOV P1,#0EFH
	;CLR P1.4
	JB P1.3,NEXT13
	JNB P1.3,$
	MOV A,#0CH
	LJMP EXIT1
NEXT13: JB P1.2,NEXT14
	JNB P1.2,$
	MOV A,#0DH
	LJMP EXIT1
NEXT14: JB P1.1,NEXT15
	JNB P1.1,$
	MOV A,#0EH
	LJMP EXIT1
NEXT15: JB P1.0,NEXT16
	JNB P1.0,$
	MOV A,#0FH
	LJMP EXIT1
	;;;;;;;;;;;;
NEXT16: LJMP REPEAT   ; DEFAULT
	;;;;;;;;;;;;
EXIT1:	RET
;;;;;;;;;;;;;;;;;
LOOK_UP:
;;;;;;;;;;;;;;;;;
	INC A
        	MOVC A,@A+PC
	RET
TABLE:  DB 0xC0,0xFC,0x92,0x98,0xAC,0x89,0x81,0xDC,0x80,0x88,0x84,0xE1,0xC3,0xB0,0x83,0x87 ;COMMON ANODE DISPLAY
;;;;;;;;;;;;;;;;;
MAIN:
;;;;;;;;;;;;;;;;;
AGAIN:	MOV P1,#0x0F
RPT:	MOV A,P1
        	CJNE A,#0x0F,GET_KEY
	LJMP RPT
GET_KEY:LCALL KEY_PRESSED
	LCALL LOOK_UP
	MOV P0,A
	LJMP AGAIN
	END