vargai
have a read of the first post:
M751 {Dxxxx, Exxxx} sets your maximum spindle rpm (Dvar) and sets your Spindle Surface Speed in UNITS per min (note this is not feet or meters per min!!!, so if you desire 200 meters / min surface speed, set E200000, sorry I could not come up with a way to know if the machine was in metric or imperial, hence followed the standard that the machine is just set in "units"
There are 3 macros.
two are called macros and one is a macroloop which does the updates of the spindle speed
The only parameters you need to give the macros as Dvar and Evar which are the maximum permitted spindle speed {to avoid overspeeding the spindle} and the Evar which is the desired surface speed.
Deszoe + Vmax have been talking about the macroloop which updates the wrong DRO {its a read only DRO which I did not know}