Pinout for 485 Null-Modem Cable

Publish Date: Feb 08, 2018 | 2 Ratings | 5.00 out of 5 | Print

Overview

This article explains the 485 null-modem cable pinout and tells how to communicate port to port using RS-485.

1. Introduction

Communicating port to port using RS-485 is possible with a 485 "null modem" cable. In this cabling configuration, the TX+/- must be connected to the respective RX+/-. The RTS from one side must be connected to the CTS on the other side. The DB-9 pin-to-pin connection is as follows:

 

Port 1 Port 2 Comments on connections
1 1 (GND)
2 3 (CTS+ : RTS+)
3 2 (RTS+ : CTS+)
4 8 (RXD+ : TXD+)
5 9 (RXD- : TXD-)
6 7 (CTS- : RTS-)
7 6 (RTS- : CTS-)
8 4 (TXD+ : RXD+)
9 5 (TXD- : RXD-)

 

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