Control.com - Nerds in Control

I need to convert Modbus-RTU (RS232) to Modbus-TCP.

Is it possible to use any RS232 to TCP converter or should I use a specific converter for Modbus?

I know that there are some converters in the market that are specially designed for Modbus. However there are other devices like MOXA NPort S 8455, that it is not stated in the manufacturer information.

Modbus over TCP is what you get when you use a straing serial to ethernet converter. This is different than Modbus TCP which has a specialized header for message synchronization. For straight Serial to Ethernet converters you need to use products that support encapsulation (See Kepwares Modbus RTU Serial server).

Modbus Ethernet to Modbus Serial converters will convert the Modbus Ethernet request to a Modbus RTU Serial request and pass it through.

A key difference is that You can only have one Modbus Master in straight Serial to Ethernet conversion. However if you use Modbus Ethernet to Modbus Serial Protocol converters you can typically have up to ten Modbus Master device connected to it.

Fred Loveless
Applicaitons Manager
Kepware Technologies
http://www.kepware.com

I use a B&B ESP901 Single Port RS-232/422/485, as an example, and it can be used with any protocol you want.

Francisco -

Modbus TCP is not the same Modbus RTU encapsulated in a TCP/IP packet. So, instead of a general purpose RS-232 to TCP converter (or Device Server) you will need a device with support for conversion between these two protocols. Often, these units are referred to as a Modbus Gateway.

In addition to offerings from my company (EKI-1221 for 1-port RS-232/422/485), there are many other suggestions from others that can be found by searching this list.

Paul Wacker
Product Manager (ICOM)
Advantech Corp.