// ATtiny85  1 LED  external event 
#include<avr/io.h>
#define F_CPU 16500000UL
int i=0;

void counter_setup() 
{
  DDRB= 0b00001011; 
 //(1<<PB1)|(1<<PB0);
  TCCR0A = 0X00;               //TCCR0A to low for normal port operation and mode 0.
  TCCR0B = 0X00;                //WGM02=0
  TCCR0B |= (1<<CS02)|(1<<CS01);    //CS02=1, CS01=1 CS00=0 Clock on falling edge
  TCNT0 = 0x00;       //initializing the counter to 0
}

void  counter_reset()
{
  TCNT0=0x00;       //reset value to 0 
  i=0;
}

int main() 
{
 counter_setup();
 while(1)
 {
  i=TCNT0;
  if ( i>=10&&i<30)           // First 10 counts
   { 
      PORTB |= (1 << PB1);   //light up LED in PB1   
                     //reset counts
   }
  else if ( i>=30&&i<40)           // First 10 counts
  {

    PORTB|=(1 << PB0);    //light up LED in PB0 
     PORTB &= ~(1 << PB1); // PBb1 Low logic at output      
    //counter_reset();
 }
  else if ( i>40)           // First 10 counts
  {

    PORTB|=(1 << PB3);    //light up LED in PB3 
     PORTB &= ~(1 << PB0); // PBb0 Low logic at output      
   // counter_reset();

  }

    

  } 
  }