Generate 1MHZ clock signal for MOS 6581 (SID)

[nickgammon]

Someone double check me on this, I don't have a good way to verify, but I think this will do the trick with no additional hardware.

//Use Timer/Counter1 to generate a 1MHz square wave on Arduino pin 9.
//J.Christensen 27Apr2012

void setup(void)
{
    DDRB = _BV(DDB1);                  //set OC1A/PB1 as output (Arduino pin D9, DIP pin 15)
    TCCR1A = _BV(COM1A0);              //toggle OC1A on compare match
    OCR1A = 7;                         //top value for counter
    TCCR1B = _BV(WGM12) | _BV(CS10);   //CTC mode, prescaler clock/1
}

void loop(void)
{
}

Yep, that generates 1 MHz square wave.