Idea of master/slave serial comm.

[T.Jackson]

But, without HPWM, how can this be possible? I'm asking that because the PWM Pin is connected to a CC motor and it must be ON all the time.

If things are happening fast enough it's possible without HPWM or USART. Certainly not ideal though nowadays, but if you can do it without them, you lend the project to be able to utilize some of the smaller & cheaper controllers that don't have HPWM & USART available.

How do you think the Z80 & 8086 controllers managed to do stuff like this? (All software-based)