Where does logic power come from if using a voltage regulator and USB connection?

I ordered a Smoothieboard that came with a voltage regulator already soldered to the board. I intend to use the board with the USB connected to my computer for most of the time. I was just curious as to where the power for the logic circuitry will come from if both are present. I would prefer it came from the USB connection as I think the power supply that came with my laser cutter might already be pretty close to its limit, still checking on that though. Thanks!

It comes from whichever has the highest voltage ( often the vreg ). I have added information about this on the 5V power part of the guides in the smoothie documentation.


Thanks, Arthur!