m_hw_timer.asm

.macro SETUP_TIMER0
.equ TimerTOP = MainClock/256/@0		; TOP counter value formula, @0 - Hz requested

	clr GREG		
	sts TCNT0, GREG

	outi OCR0A, low(TimerTOP)	; set OCR0A - TOP value 
	sti TIMSK0, (1<<OCIE0A) 	; set OCIE0A - unmask interrupt 
	outi TCCR0A,(2<<WGM00) 		; enable CTC mode 
	outi TCCR0B, (4<<CS00)		; set prescaler
.endmacro


; Clock Select Bit Description (TCCR0B)

; CS02 	CS01 	CS00 	Description
; 0 	0 	0 	No clock source (Timer/Counter stopped)
; 0 	0 	1 	clkI/O/(No prescaling)
; 0 	1 	0 	clkI/O/8 (From prescaler)
; 0 	1 	1 	clkI/O/64 (From prescaler)
; 1 	0 	0 	clkI/O/256 (From prescaler)
; 1 	0 	1 	clkI/O/1024 (From prescaler)
; 1 	1 	0 	External clock source on T0 pin. Clock on falling edge.
; 1 	1 	1 	External clock source on T0 pin. Clock on rising edge.