The P212S is a Supervised Power Supply which is considered an M1 Bus Device (Type 1 = keypad) and will connect to the M1’s Bus the same way as any other bus device. It is also possible to use the P212S as a standalone power supply and not supervised. The Home Run to the Shop you plan on connecting the P212S, M1XIN and M1XOVR to the M1DBH using Cat5/6 and then power the the M1XIN and M1XOVR from the P212S? In this scenario it doesn’t matter which Port the P212S is connected. I would suggest you connect Data A, Data B and NEG from the M1’s RS485 terminal to the Data A, Data B and NEG on the M1DBH then power the M1DBH +12 and NEG (screw terminals) from the DC Output from the P212S. Connect the P212S, M1XIN, M1XOVR to the M1DBH using Cata5/6 following the instruction on page 12 and 13 of the M1 Installation Manual.