well, in the event anyone is interested, or might need this info in the future.. by accessing the ramping flag (on the plx20/51, terminal 23), spindle @ speed can be determined. The ramping flag, by default goes high while the spindle is ramping up to speed, and low when the spindle is at speed. If an active high output is desired, change the DOP2 invert mode (pin 266) to INVERT.
This all assumes the internal ramping function of the drive is being used.
(info obtained from Bardac Tech Support).