Modbus RS485 connection

M12 circular connector

The M12 socket is inverse coded, and has five pins. Pin 1 is 5 VDC and 3 is GND for the active termination resistor. These must never be misused for other functions, as this can lead to destruction of the device. Pin 2 and pin 4 are the Modbus signals. These must never be swapped over, as this will prevent communication. Pin 5 is the shield, and this is capacitatively coupled to the Fieldbus Box chassis.

M12 socket pin assignment

Type

M12

9 pin  D-Sub

+5 V DC

Pin 1

Pin 6

TxD/RxD

Pin 2

Pin 3

GND

Pin 3

Pin 5

RxD/TxD

Pin 4

Pin 8

Shield

Pin 5

D-Sub female connector (case)