I am designing a system based on this application note of TI. The overall design goal is to have multiple shift registers, connected via RS-422 and ethernet cables over fairly long distances(up to 5 meters between each node). Each node should convert the differential RS-422 signal to SPI for the shift register and after that back to differential the RS-422 for daisy-chaining nodes. Each node can have a single power supply or - if spatial possible - share a power bus with neighbouring nodes.
My plan is to have MOSI,MISO and CLK as differential signals in a twisted pair, since they will have the highest data rate(not specified yet). Using standard ethernet cables this setup will use 3 of 4 twisted pairs. This leaves me with one twisted pair.
For clean initial conditions I would like to have STROBE/LATCH and OUTPUT_ENABLE for clean operations as control signals. Is there any problem using the remaining twisted pair non-differential for the control signals?