; Strobe Experiment
; Low duty cycle lighting.
;


	INCLUDE	"P12F509.INC"
	INCLUDE	"macross12f509.inc"


; Self running, no watchdog...
	__CONFIG _MCLRE_OFF & _CP_OFF & _WDT_OFF & _IntRC_OSC


	; available file registers 0x7-0x1f (25 registers)
	; (there are more at 0x30-0x3f but only by
	; FSR indirect addressing.)	
	CBLOCK	0x07
	t1,t2,t3
	pix
	
	CBLOCK07 ; last
	ENDC

	IF CBLOCK07 > 20
	ERROR "CBLOCK07 exceeded"
	ENDIF
	
	
	ORG		0
	GOTO	Start

Slow:
	DECFSZ	t1,f
	GOTO	Slow
	DECFSZ	t2,f
	GOTO	Slow
	DECFSZ	t3,f
	GOTO	Slow
	RETURN

DELAY MACRO	time
	MOVLF	((time >> 0) & 0xff) + 1,t1
	MOVLF	((time >> 8) & 0xff) + 1,t2
	MOVLF	((time >> 16) & 0xff) + 1,t3
	CALL	Slow
	ENDM
		
Start:
	; All five outputs to "out"
	; GPIO 3 can only be "in"
	MOVLW	0
	TRIS	GPIO
	MOVLW	b'11011111' ; 0xDF, internal timer, no pullups, slowest watchdog
	OPTION


	MOVLF	0xAA,pix
	
Ere:
	MOVFF	pix,GPIO

; Oscillator runs at 4mhz
; Instructions take 4 cycles each
; Delay loop uses ~3 instructions/tick
;
; So, Delay time for X fps is 1000000 / (3 * X)
R	EQU		10904
;T	EQU		21808   ; total count for 15fps
;T	EQU		13889	; 24 fps
T	EQU		1000000/(3 * 28)

Ton	EQU		T/8
Toff EQU	T - Ton

A:
	MOVLF	0xff,GPIO
	DELAY	Ton
	MOVLF	0,GPIO
	DELAY	Toff
	GOTO	A
	
	
	MOVLF	((R >> 0) & 0xff) + 1,t1
	MOVLF	((R >> 8) & 0xff) + 1,t2
	MOVLF	((R >> 16) & 0xff) + 1,t3
	
	CALL	Slow
	INCF	pix,f
	GOTO	Ere
	GOTO	Ere

	END