[jlobin]

In the UHU Manual for the original controller it says "The controller does a 4-fold interpretation of the encoder lines"

Exactly what does that do to, say a 900 ppr encoder signal, and what effect does the M command have on that?

Thank you,

Jack

[Al_The_Man]

I am assuming they do what most controllers do is detect the four edges of the two quadrature pulses to multiply the basic resolution count x4.
So 900ppr would equal 3600 pulses resolution.
Al.

[LZ1TWB]

See this, copied from the UHU manual:

Step multiplier (M)
The provided integer value is added supplementary with every step pulse. I.e. if 'V' is set to '2', the motor moves exactly three 4-fold interpreted encoder lines with every step pulse. This makes it possible to drive setups with high encoder resolutions to high speeds even if the commanding PC is limited in Terms of stepping rate. As it also reduces overhead operations, it is always desirable to increase this parameter if the resolution of the encoders is not needed. Attention: Setting 'V' to a high value leads to higher tracking errors with every step. The tracking error shutoff 'F' has to be increased accordingly. Useful values are 0 to 20.

So, if your encoder is 4*900 = 3600ppr with M set to 1, you need 1800 pulses from the computer to spin it 1 rev.

If you change this value, you need to recalculate the 'pulses per mm/inch' value in the control software.