84. Timer Modes

An external signal of 5 kHz is applied to digital pin 5 (Timer 1) of Arduino UNO. What will be the status of LED? (after executing the following code)

Code:

const int ledPin = 8;

void setup() {
  pinMode(ledPin, OUTPUT);

  // Configure Timer1 for normal mode
  TCCR1A = 0;
  TCCR1B = 0;
  TCNT1 = 0;

  // External clock source on T1 (rising edge, no prescaler)
  TCCR1B |= (1 << CS12) | (1 << CS11) | (1 << CS10);

  // Clear overflow flag initially
  TIFR1 |= (1 << TOV1);
}

void loop() {
  // Wait here until the overflow flag is set
  while (!(TIFR1 & (1 << TOV1)));
  TIFR1 |= (1 << TOV1); // Clear the flag
  digitalWrite(ledPin, !digitalRead(ledPin));  // Toggle LED
}