Re: motor interface wiring

[Mark Rivers <RIVERS@cars3.uchicago.edu>]

> Tim Mooney writes:
> I think this is overkill, but I see no point in excluding it.
> It's the driver's responsibility to stop on an open limit switch.
> Sending the controller an unsolicited message that the driver screwed
> up is not a robust way of getting the motor stopped.  (If you don't
> trust the driver hardware to respond to the limit switch, why would you
> trust it to tell you it didn't?)

Actually it is generally the CONTROLLER'S responsibility to stop sending pulses
on an open limit switch. This is certainly the way the current Step-Pak
drivers work - they don't look at the limit lines at all, they only pass them
back the controller.

> This signal will probably not be delivered by name from the Step Pack
> interface, since it gets only one home signal from the motor
> connector.  However, Leo Bric plans to use DB-9 connectors for the
> encoder inputs, and since only eight signals are currently specified,

I want to second Gerd's recommendation. Klinger/Newport stages with encoders 
and origin signals use the following signals:
    Phase A
    Phase B
    Index (also called Top 0)
    Origin (Home)

Home can be established to within 1 step by looking for the 0-1 transition on
Origin and then looking for the next Index pulse. This is 0.1 micron on their
best stages.

Note that their stages also require a +5V input to drive the origin and
encoder electronics. Leo must provide us with an option for this. It should
not be constrained to be the same voltage as the motor drive.

Mark