Count Arduino PWM frequency by other Arduino board

I have two Arduino UNO. First Arduino generate PWM at pin 9. I need to connect this PWM output to second Arduino and calculate frequency.
For example: if I set on first arduino analogWrite(9, 0), analogWrite(9, 128), analogWrite(9, 255) I want to know this value on second arduino.
Is it possible? If I want measure 3 pwm is possible too? Arduino have only 2 hw interrupts.

The frequency of the PWM signal is fixed. The width of the pulse varies. Is the width what you want to measure? Use pulseIn() to measure pulse width, no interrupts required.