> Wow, I never used such a stepper motor. The most a 0.9 =BA/step wich
> gives 400kHz. Really need a 50 MIPS micro ONLY for a stepper?

Yes. Although the speed of the SX was really needed because the pulse
timing loops used varying 16-bit data. The actual maximum pulse frequency
was 250kHz IIRC

It was for a stabiliser. As the gyro moved, an 18F measured the pitch
and roll angular differences and did the maths, the result of which was
the number of microsteps the motors had to move to keep a platform
horizontal. These numbers were sent to the SX, which used them in the
pulse timing loops. I wrote isochronous code which broke down into
fixed-cycle modules and everything meshed together very well with PIC-
SX handshakes, data being transferred into a buffer during loop time.
Even so, it was tight, with every SX cycle accounted for =


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