;************************************************
; written by :	John Morton			*
; date : 21/09/97				*
; version : 1.0					*
; file saved as : Diamond			*
; for PIC508					*
; clock frequency : (internal )   =  4 MHz	*
;************************************************

; PROGRAM FUNCTION :  To act like diamond brooch by randomly flashing LEDs

 		list 	     	P=16Cxx
		include		"c:\pic\p12c50x.inc"

;============
; Declarations :  

		OffTimer	equ	08
		
#define	Tilt	GPIO, 3	

		org		0
		movwf		OSCCAL	; calibrates internal oscillator
		goto		Start


;===========
; Subroutines : 


Init		clrf		GPIO		; resets general port
		movlw		b'001000'	; GP0 - 2, 4 : LEDs, GP3 : tilt
		tris		GPIO		; GP5 : not connected
		movlw		b'00000111'	; sets up TMR0
		option

		retlw		0

Timing		movfw		TMR0		; has 1/10th of a second passed?
		btfss		STATUS, Z	; 
		goto		Timing		; no, so keeps looping
		incf		TMR0		; yes, stops multiple zero read
		retlw		0		; returns

;=============
; Program Start : 

Start
		call		Init		; sets up inputs and outputs
Main		call		Timing		; waits for 1/10th of a second
		movlw		d'27'		; changes LEDs
		addwf		GPIO		;  
		btfsc		Tilt		; has tilt signal been received?
		clrf		OffTimer	; yes, so resets Off Timer
		decfsz		OffTimer	; no	
		goto		Main		;
		clrf		GPIO		; turns all LEDs off
		sleep				;
		goto 		Main		; loops back up to Main		

END