Well, I'm hitting the buffers again trying to get Mach3 to control the servo system.

Having got the Yaskawa software to power up the motor and drive it at various speeds it seems that fundamentally the drive and motor are sound. However, the drive does do something weird. Having set the parameters all back to factory settings I then set the Cn-01 bit 0 to 1, which switches the motor on at start up without any external commands. All good except the motor rotates at around 1-2rpm. Changing the direction parameter changes the direction of rotation. I can't see what command is causing the rotation. If Cn01 bit 0 is changed back to 0 and the motor jog test performed the motor remains locked in position until commanded to run forward or reverse. I did wonder if it was interference on the encoder cable (the temporary set up is using shielded but not twisted pair cable), but this doesn't fit with the jog test results. Both the drivers I have do the same thing.

I found the following instructions on another forum:

This is just for the SGD and SGDA type P Yaskawa Servos to get the very minimum wiring to give Pulse and Direction control. The only signals you have to have on 1CN are pins 1, 2, 3 & 4. To use this minimalist configuration, set parameter Cn-01 to 0000 0000 1010 1101 or AD hex. Set Cn-02 to all zeros, or 00 hex. This means the drive will power up in the on state and won't be looking for or caring about overtravel switches. To clear a fault, power down and back up.

Now tie 1CN pins 2 & 4 to common (0 Volts) of the printer port (PP) or breakout board (BOB) and pin 1 to the step output of the PP or BOB through (in series with) a 180 ohm 1/2 watt resistor. 1CN pin 3 ties through a 180 ohm resistor to the direction output.
Apart from the fact that the parameter instructions don't quite make sense, if I use either of the Cn-1 settings which switch the motor on at start up, a Mach3 command to rotate in the forward direction causes the motor to run at 2480 rpm (or thereabouts) and a reverse command causes the motor to stop, well, almost stop - it does the 1-2rpm thing instead.

One other interesting observation: if power to the breakout board is switched off Mach3 commands still do the same as above but at 1109 rpm and 1rpm

I have to say that I've never come across a more opaque manual - I've read and read and still can't fathom what parameters need to be changed to get sensible functioning.