eric1_stop_clock

// stop CPU clock in high state
void stopClock() {
	// wait for clock to go low
	while((PIND & CPU_CLOCK) != 0) {}
	// wait for clock to go high
	// must check that WE is high, otherwise CPU may be writing to memory
	while((PIND & (CPU_CLOCK|SRAM_WE)) == 0) {}
	TCCR2B = 0;	// stop timer by setting prescaler to 0
	TCCR2A = 0;	// disable timer so that we can control PD7 manually
}