RS-485 is a differential signaling, half-duplex multi-point communication standard, typically using a pair of twisted-pair cables (two-core wires) for data transmission. Detailed connection steps for connecting a serial device to the RS-485 interface of a Moxa device are as follows:
Step 1: Confirm Device Interface and Pin Definitions
Pin definitions may differ between different brands of devices. It is recommended to contact the corresponding manufacturer to confirm the correct pin definitions before wiring!
MOXA products mainly have the following three types of serial ports:
DB 9 interface wiring sequence and applicable models are as follows:
RJ 45 interface wiring sequence and applicable models are as follows
Terminal interface wiring sequence and applicable models are as follows:
Step 2: Connect Using Cables
Scenario 1: Connecting a Moxa device to a single RS-485 device. When connecting a Moxa device and a serial device, connect the positive (B) pins to positive (B) pins and the negative (A) pins to negative (A) pins.
Scenario 2: When connecting a MOXA device to multiple RS-485 devices, a daisy-chain connection must be used. All devices' A(+) terminals are connected in parallel to the positive bus line, and all devices' B(-) terminals are connected in parallel to the negative bus line.
Scenario 3: Termination resistors need to be added. If the NPort has a built-in termination resistor (e.g., the NPort 5450's built-in termination resistor can be opened via a DIP switch (usually SW 3 is the termination resistor switch), then only a termination resistor needs to be added at the end of the link, as shown in the diagram below.
Scenario 4: If the NPort does not have a built-in termination resistor, it can be added on both sides of the RS-485 link, with the wiring shown in the diagram below.
Post time: Apr-29-2026