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#INCLUDE	'A:\VAR_DEF.ASM'

*LAB3-EX2

* Define program variables
	ORG	DATA
DT	RMB	2	; Half wave duration

* Start main program
	ORG	PROGRAM
START	LDX	#REGBAS
	LDAA	#%00010000 ; mask for OM3=0, OL3=1 
	STAA	TCTL1,X	   ; set OC3 to toggle
	LDD	DT	   ; store TCNT+DT in TOC3
	ADDD	TCNT,X
	STD	TOC3,X

* Main loop
LABEL1	LDAA	TFLG1,X	   ; check OC3F
	ANDA	#%00100000 ; mask for OC3F
	BEQ	LABEL1	   ; loop back

* We are here when output compare happens
	LDAA	#%00100000 ; reset OC3F
	STAA	TFLG1,X
	LDD	DT	   ; add DT to TCNT
	ADDD	TCNT,X	   ; 
	STD	TOC3,X	   ; store new time in TOC3
	BRA	LABEL1	   ; back to the top
	SWI

	ORG	RESET	; reset vector
	FDB	START	; set to start of program