Re: Stepper Motor
Stepper motors can be classified into unipolar and bipolar.
Bipolar ones have simple windings, just 2 wires per winding. Thus they make better use of the available winding area and produce more power. However, to drive them you need to be able to reverse the voltage across the windings, which means more complicated drivers. The chips you mention are designed for such motors.
Unipolar ones have center-tapped windings, that is they use 3 wires per phase (winding). The center tap is connected to a voltage source and the ends of the winding are driven by transistors. Thus, no voltage reversal is needed. But the available power is lower and the stress on the transistors is twice the supply voltage.
The 4-wire motors you have are most likely bipolar ones, having two windings (phases). The 5 and 6-wire ones could be unipolar. Thus, you can have a common center tap and 4 wires (2 windings) or you could have 2 ceneter-tapped windings, each with its common plus 2 wires (although the 6-wire ones ccould be different).
The only way to know for sure is to measure with an ohmmeter and tell which wires are connected to the same winding and by measuring the resistances actually tell which are the center-taps, if any.