// blink.c compiled with CodeVisionAVR 1.0006
// Wichit Sirichote 26-02-43

#include <90s8535.h>
#include <delay.h>    
#define xtal 8000000                           

unsigned char counter1,flag1;
bit enable_tone,off_hook;

void tick_wait(){
        
	while((TIFR&0x01) == 0); //cputick <10);
			TCNT0 = 256-75; //78;		// reload timer 0 for 100Hz tick generation		
			TIFR |= 0x01;		// clear Timer 0 overflow flag by writing '1'
}
			    
void task1(){
	counter1++;
	if (counter1 >100)
	{PORTC ^= 0x80;
	 counter1 = 0;
	 flag1 ^= 0x01;  // toggle flag1.0
	 enable_tone ^= 1; // toggle enable_tone bit
	 }
}	 
     
void on_tone(){
	TCCR2 = 0x1e;  // enable OC2 toggle for tone generation
}

void off_tone(){
	TCCR2 = 0x2e;  // turn OC2 low
}
	                                  
void test_tone(){
	if (enable_tone == 1) //((flag1&0x01) != 0)
		on_tone();
		else off_tone();
}			                                                              

void main()
{        
// initialize corresponding port 
		DDRA=0x00;		/* all port A is input  */
		DDRB=0xff;		/* all port B is output */
		DDRC=0xff;		/* all port C is output */		
		DDRD=0x80;      /* port D is input except PD7 for OC2 output  */
		PORTB=0x00;   
		PORTC=0x00;    
		
		flag1 = 0;
// timer0 is used for system 10ms tick				                             
		TIMSK = 0x01;           // Timer 0 overflow enable
        TCCR0 = 0x05;          // Start Timer0 with clk/1024        
// timer2  is used for 550Hz tone generation, the real output measured via Fluke83 is 558Hz        
        OCR2 = 28;			//  toggle oc2 every 1/1116Hz or 558Hz output frequency 
        TCCR2 = 0x1e;       // start timer2 with PCLK/256, reset timer2 when matched

		while (1)
		{                       
		    tick_wait();	// 10ms tick 
            test_tone();
            //on_tone();                                         
			task1();		
    
		}
}