To read PWM signal with pulsein

Hello everyone i have just started to use arduino. I would like to read clock pulse from PWM pin with pulseIn command for per second. For example, when I assign the value 255 to the pwm pin, I want to read the value 255 with the pulseIn command in serial port screen. I would be very grateful if you could share a sample code.

...the PWM goes HIGH.
Permanently.

When I assign the value 255 to the pwm pin, I think it takes the high value 255 times per second. I didn't understand how it is permanently high.

I think you're confusing duty cycle with frequency.

On the AVR, analogWrite (pin, 255) is equivalent to digitalWrite (pin, HIGH).

Easy enough:

const unsigned long TIMEOUT = 10000; // 10 millisecond (100 Hz) 

const byte PWMPin = 3;
const byte InputPin = 4;

int readPWM(int pin)
{
  unsigned long highDuration = pulseIn(pin, HIGH, TIMEOUT); 
  unsigned long lowDuration = pulseIn(pin, LOW, TIMEOUT);

//  Serial.print(highDuration);
//  Serial.print(", ");
//  Serial.print(lowDuration);
//  Serial.print(" -> ");

  if (highDuration == 0 || lowDuration == 0)
    return digitalRead(pin) == HIGH ? 255 : 0;

  return (highDuration * 255) / (highDuration + lowDuration);
}

void setup()
{
  Serial.begin(115200);
  delay(200);
  
  pinMode(InputPin, INPUT);

  for (int i = 0; i < 256; i++)
  {
    analogWrite(PWMPin, i);
    delay(1);
    Serial.print(i);
    Serial.print(" -> ");
    Serial.println(readPWM(InputPin));
  }
}

void loop() {}