I have put together a unipolar board using the L297. I basically looked at the spec sheet and went from there. I would like to know how you arrive at the optimum frequency for the input of the ossilator pin (16). I know there is a better way than the trial and error method I used with the bread board. I have soldered up 2 of these boards and am drivng PK264-01A Vextra motors @ about 1000 rpm with no problem.