I have heard of this Drive system before, unfortunately i do not know any controller software that supports this directly.
I could think of two ways to accomplish this tho.
1) Earlier releases of Turbocnc support a Phase drive system a modefication of this should be relative easy because the source code for this is included with the purchase of this Software.
2) Design of a electronic gadet to convert the step and direction signal to a Left and right Pin output depending on the current setting of the direction Pin.
I am not a electronics guy but for some of the wizards here this should be rather easy to rig up with some logic gates.
Maybe there is a product for this allready out there?