current set resistor

Hi,

In the unipolar drives, the current limiting resitor is used to limit
the current to the motor when back emf is zero or very low. Knowing
this it is easy for one to calculate what resistor to use given the
coil resistance.

I hope to understand the use of the current set resistor for the
gecko stepper drive. Is the current set resistor put there to "sense"
when current need to be chopped off or something? Understanding it
will make one more confident in calculating a suitable resistor to be
used with a particular motor, rather than just plugging specs into a
given formula without understanding the formula

R = (47,500 * I)/(7 - I)

It would help to know where the 47,500 and the 7 came from. What
should one do, for example, if the motor rated current is 7 amp (R =
infinity) keep the teminals 11 and 12 open?

Thanks

Peter