;PIC12F629.asm
	;CODE PUZZLE - Detects buttons A and B


	list	p=12F629
	
	include	"p12f629.inc"

	__CONFIG	_MCLRE_OFF & _CP_OFF & _WDT_OFF & _INTRC_OSC_NOCLKOUT  ;Internal osc.

	
			; globals

fileA	equ		26h
fileB	equ		27h	
fileC	equ		28h
fileD	equ		29h
fileE	equ		2Ah
	


status		equ	03h
option_reg	equ 81h


Start	org	0x00		;program starts at location 000
		nop
		nop
		nop
		nop		;NOPs to get past reset vector address
		nop
		nop


SetUp	bsf		status,rp0 	;Bank 1	
		movlw	b'10000110'	;Turn off T0CKI, prescale for TMR0 = 1:128
		movwf	option_reg    
		bcf	status,rp0		;bank 0  
		movlw   07h         ;Set up W to turn off Comparator ports
		movwf   CMCON       ;must be placed in bank 0   
		clrf 	GPIO       	;Clear GPIO of junk		
		goto 	Main	
		

LED0	bsf		status,rp0  	;Bank 1	
		movlw	b'00111111'		;make all input
		movwf	TRISIO	    	;turn off all LEDs
		bcf		status,rp0		;bank 0 
		retlw	00		
		
		
LED1	bsf		status,rp0  	;Bank 1	
		movlw	b'00111001'		;make GP1,2 output
		movwf	TRISIO	    	;enable outputs	
		bcf		status,rp0		;bank 0 
		movlw	02h				;make GP1 HIGH, GP2 LOW
		movwf	GPIO 			;turn on LED1
		retlw	00
	
	;Delay 0.5 sec

Del_1	movlw 	02h
		movwf 	fileC	
DelX	decfsz 	fileA,1		; ,1 denotes the result of the decrement 
		goto 	DelX	
		decfsz 	fileB,1		;     is placed in the file	
		goto 	DelX
		decfsz 	fileC,1
		goto 	DelX
		retlw 	00
		
		;test program to detect switch A and switch B and tell them apart!!
		
	
Switch	bsf		status,rp0 		;Bank 1	
		bCf		TRISIO,0	   	;make GP0 output	
		bcf		status,rp0		;bank 0
		bcf		GPIO,0			;make switch-line LOW
Sw1		decfsz 	fileA,1			; short delay while 100n discharges
		goto 	Sw1	 
		bsf		status,rp0 		;Bank 1	
		bsf		TRISIO,0	   	;make GP0 input	
		bcf		status,rp0		;bank 0
		movlw	01
		movwf	fileB
Sw2		movlw	0D0h
		movwf	fileA
Sw3		decfsz 	fileA,1			; delay while 100n charges via switch
		goto 	Sw3	
		decfsz 	fileB,1
		goto 	Sw2		
		btfsc	GPIO,0			;is switch-line HIGH?
		retlw 	01				;yes - switch A pressed
		retlw	00				;no
		
							
	
Main	call	Switch		;see if button A is pressed
		movwf	fileD		;put result of switch into file D
		btfss	fileD,0		;
		goto	Main
		call  	LED1		;turn on LED 1
		call 	Del_1
		call  	LED0		;turn off LED 1
		call 	Del_1
		goto	Main
		
							;Results: B is just at the point of detection 
							; with 2 x fileB and fileA = 0FFh. 
							; Use 1 x fileB and fileA = 0FFh
							;Button A is not detected with fileA less than D0h
							;and 1 x fileB
							;Use 2 x fileB and fileA = 0Ah
			

	end