void timer1CTC_Init(int max_count, int my_div) {
 TCCR1A = 0;
 TCCR1B = 0;
 // clear all bits
 // clear all bits
 OCR1A = max_count- 1; // maximum count- 1
 TCNT1 = 0x0;
 TIFR1 = 0x7;
 TIMSK1 = 0;
 TCCR1B |= 0x8;
 if (my_div == 1) {
 // reset counter
 // clear all interrupt flags
 // disable all interrupts call to MCU
 // set WGM12 to 1, mode 4 CTC
 TCCR1B |= 0x01; // set CS to dividy clk by 1
 } else if (my_div == 8) {
 TCCR1B |= 0x02; // set CS to dividy clk by 8
 } else if (my_div == 64) {
 TCCR1B |= 0x03; // set CS to dividy clk by 64
 } else if (my_div == 256) {
 TCCR1B |= 0x04; // set CS to dividy clk by 256
 } else if (my_div == 1024) {
 TCCR1B |= 0x05; // set CS to dividy clk by 1024
 }
 }
 
 void setup() {
 DDRB = 0xF0;
 // set PB7:4 to output
 PORTB &= 0x0F; // clear PB7:4
 // set timer 1 count frequency to 2 Hz (0.5 second)
 // by counting 31250 times at 62500 Hz (16 MHz divided by 256)
 timer1CTC_Init(31250 ,256);
 }
  void loop() {
 
 if (TIFR1 & 0x2) { // check OCR1A match interrupt
  }
 TIFR1 = 0x2; // clear OCF1A match interrupt flag
 PORTB ^= 0x80; // toggle PB7
 }