Again, we cannot send our PWM *data* directly to the floppy-drive's /Write-data pin. Instead we need to send two falling-edge pulses for each PWM-nibble. Confusingly, I plan to use a PWM-output from the microcontroller to create those *two* precisely-timed falling-edges. Thus requiring *two* uC-PWM cycles to write *one* PWM-nibble to disk.

In order to write the PWM-data, I've come up with a couple possibilities: 

In both cases, the negative-going /WR pulses will vary in duration depending on the value of the PWM-nibble to be written. This shouldn't matter, as the flux-transition is triggered by the falling-edge.

The second case is a little less-intuitive, as the PWM-output cycle starts midway through the PWM-data signal.

Importantly: the PWM-signal will have a constant period, possibly saving several instruction-cycles, which may be near the limit.

These cases both assume a PWM-output that starts high and goes low after a set duration... AVRs allow for the opposite, or it could easily be done with an inverter, but I've yet to analyze whether that could be helpful (e.g. in aligning a *data* start with a *signal* start?). My intuition is that doing-so would require both PWM-output cycles to vary in period, e.g. duration1=value, duration2=2us-value, eating into our valuable instruction-cycles.