Volume Zapper

#include "qc.h" 

//these are the timer registers
#define TCR_0 (*(unsigned char *)0xffc8)
#define TCSR_0 (*(unsigned char *)0xffc9)
#define TCORA_0 (*(unsigned char *)0xffca)
#define TCORB_0 (*(unsigned char *)0xffcb)
#define TCNT_0 (*(unsigned char *)0xffcc)
#define STCR (*(unsigned char *)0xffc3)

int main()
{
	int j;
	unsigned char bZap, bDelay;

	LCDPrints(" READY");
	
	//give some control so we don't have to keep removing the batteries
	while (getc()==RUN)
	{
		LCDPrints(" RUN");
		
		//turn off all interupts
		  __asm__ ("\torc #0x80,ccr\n");

		//Set the Timer Control Register 0 to 0 so nothing happens while we set things up
		TCR_0=0;

		//set the clock to increment the counter every 8 clock cycles - very quick!
		STCR &= !0x01; //clear bit 0 of the STCR
		TCR_0=9; //set bit 0 for 2x, bit 3 for clear count on A
		//set up the output to low on compare-match A, high on a compare match B
		TCSR_0=9;
		//set TCORA_0 to 32
		TCORA_0=32;
		
		//try sound levels
		for (j=0;j<16;j++)
		{
			//set volume
			TCORB_0=j;

			//zapping sound
			for (bZap=0;bZap<255;bZap++)
			{
				//turn speaker 'sort of on' ie using our square wave
				TCNT_0=0;
				TCR_0=9;
				for (bDelay=0;bDelay<bZap;bDelay++);

				//turn speaker off
				TCR_0=0;
				for (bDelay=0;bDelay<bZap;bDelay++);
			}
		}

		//Set the Timer Control Register back to off 0
		TCR_0=0;

		//turn interrupts back on
		__asm__ ("\tandc #0x7f,ccr\n");
		LCDPrints(" READY");
	}
	LCDPrints(" DONE");
	getc();
	return 0;

}