Automatic tool change arm stepgen

I'm retrofitting a Sodick 450MC, got most of the stuff working and running up to automatic tool change part, the tool changing arm is driven by the stepper motor,
​the stepper will rotate some fix turns to change tool
So how can I config stepggen for the stepper ? btw I'm using mesa 7i95 board
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There are probably several ways of doint it, but i would stick to using a stepgen with preset values, or set the arm as U or V or W axis and use gcode to run it in the tool change macro or remap.

can you send me a sample of config file for both method?