What is the frequency range of PWM output on an Xbee WiFi module S6B using PWM?

I would like to output a square wave from an Xbee WiFi Module (S6B) and want to know what the limitations I need to be aware of. What is the frequency range I can expect to achieve with one of these devices?

At this time I am expecting to achieve this square wave via the PWM output of value X divided into the maximum switching frequency Y. The reasoning is that 50% duty cycle PWM of 1MHz will produce an adequately accurate 500 KHz squaare wave to run a piezo buzzer.

As far as I am aware, you don’t have the ability to enable the pwm output.