For pulse density modulation if X is too big – say, if you have a minimum time increment of 1 microsecond, and your period is 256 microseconds, and X is greater than 128 – the line idles ...

PDM — pulse density modulation — is similar to PWM and, ... There are several ways [Chris] could produce the output he wanted. PWM was one choice, and some example code uses a timer to do PDM.