An axis is Virtual when the ATYPE is 0 and the axis is in the processing schedule.  To add an axis to the processing schedule, simply write to any axis parameter.  For example UNITS AXIS(20) = 245 will activate the axis and  it will become a virtual axis if it is not already a real axis with a drive and motor.

Example setup:

BASE(10)

IF ATYPE = 0 THEN
    UNITS = 100

    SERVO = ON

ELSE

   PRINT #5, "Axis ";BASE;" is already allocated to a drive/motor"

ENDIF

Once an axis is inthe processing schedule, it cannot be de-activated and the controller should be re-started to remove all previously active axes.