The UNI/O protocol was created by microchip and is a 1 wire bus.
Docs
Recommended Usage of Microchip UNI/O™ Bus-Compatible Serial EEPROMs
Voltage Range
Not specified by the protocol so dependent on the devices being used.
Circuit
A pull up resistor is not required but advisable so the bus is idle if the master is not driving it. The value is dependent on bus voltage and other factors – see here. Based on the calculation is this datasheet:
5V bus, Rpmin = 15K33, Rpmax = 150K
3V3 bus, Rpmin = 9K666, Rpmax = 99K
Max cable length
We couldn’t find a reliable source of info on this. In our bench based tests, using unscreened (not a good idea!) 3 core 7/0.2mm cable, we had comms working fine over 31m. When testing at 100m comms would not work at all. This was with the bus speed set to slowest allowed (10kHz).