chessie,
You are using an external motion device and should have said so right from the get go.
Have no experience with the UC400 ETH controller. There should be a installation
and user guide available for use with Mach from the seller / manufacturer. There are product downloads available
for the 400. Did you have a read of that info?
If someone has experience with UC400 ETH they can help you and may reply
here. If not, I would suggest that you go back to the manufacturer for specifics.
The mach3 threading pdf does not address the UC400 ETH.
RICH