I just wanted to throw this up here to show an example of how the timing is working on my project. Its working well.
Top line is the input signal from the drive. Bottom line is the firing of interrupts, either from the RTCC overflowing on a regular 2us interval (actually a little less) pictured by an R, or from the falling edge trigger, with an E.
I still have issues to work out, but I’m getting closer to what I’ve set out to do.