How to control multiple stepper motors

I'm very much at the stepper learning phase ...

Using the L6470 how would you command two or three motors to work in close co-ordination. For example to get motor A to do 612 steps, motor B 476 steps and motor C 211 steps all starting and ending at the same time? (and to forestall smart-alecs, I don't mean that the start time and end time are the same :))

(I think I know how to do this with an A4988).

...R