TechTalk – Moxa MB3170 : RS485 Wiring For Old and New Model

Moxa MB31270 converts Modbus RTU (serial via P1) into Modbus TCP (Ethernet port). Note that it is not an encapsulated Modbus via TCP but a Modbus TCP itself. There is a difference between Modbus TCP and MOdbus via TCP… but it is not part of this article.

In this artice, we will demonstrate how to wire 2-wired RS485 for both newer (cyan Moxa front sticker) and older (blue Moxa front sticker) models of MB3170. See image below.

Xybernetics Moxa MB3170 - RS485 Wiring

Just remeber that if the wiring is incorrectly wired, you will get no packets (with function code 83hex) or your will get FF hex from the slave Modbus RTU with response being “RTU resp” in the Traffic Monitor tool.

The Youtube videos demonstrates how to wire below are proven and working from my profesisonal experience. Wiriing schematics are shown in the side sitcker of the Moxa MB3170.