Applications: Protocol Conversion, Modbus
Modbus as the Master

When we ask the question "What protocol is on the network?", we are really asking "who's the master?".

The first scenario is this: You have a Modbus network with a number of Modbus devices. You have a device that does not talk Modbus, but you want to integrate it into your Modbus network. In this instance, we say that Modbus is the "protocol on the network".

The second scenario is this: You have a Modbus PLC doing the primary control for your system, and may even have something like WonderWare for HMI. You do not have or need a network. You simply need to integrate one or more non-Modbus devices so that your PLC can monitor and control them. In this instance, even though you do not have a distributed network, Modbus is the protocol in charge as the master, and therefore we still call Modbus the "protocol on the network".

There are many other scenarios that are variations on these themes. The main thing to ask is, "Who's in charge" of communications. That will be the "protocol on the network".

Modbus as the Slave

Assuming you just read the column to the left, the slave would simply be on the opposite end.

Modbus is not defined as a peer-to-peer protocol. However, even if it was, we still usually have some notion of a primary controller with one or more subordinate controllers which we might refer to as "slaves". In the case of Modbus, the protocol clearly specifies one master and multiple slaves. The slave in Modbus is simply a device which responds to queries only when queried, and never generates queries on its own.

If we have a device which was manufactured as a Modbus slave, but we want it to be a slave on a non-Modbus network, this possibility is supported for several other protocols using Babel Buster gateways. When we want to put this Modbus device on a non-Modbus network, we answer "Modbus" to the question "What protocol does the device talk?"

The Babel Buster family supports Modbus devices on BACnet and LonWorks networks, and also makes Modbus devices accessible via SNMP.

Is this you looking for
a network gateway? 

You need to start with two pieces of information:
(1) What protocol is on the network?
(2) What protocol does the device talk?

Use the Gateway Chooser to guide you through the questions while you choose from available answers to arrive at a model number.


Modbus as the Master

Support for Modbus as master has been somewhat limited in the past. We are currently experiencing a markedly increased demand for Modbus as master due to increasing application of industrial PLC's in building automation. New gateways are in development to enhance our support of Modbus as master.

Support for Modbus as master for devices which are either LonWorks Free Topology or BACnet IP is currently available.

 Modbus as the Slave

Support for Modbus as slave (on non-Modbus networks) is one of the oldest and broadest branches on the Babel Buster family tree. Most combinations that one might encounter in building automation are available, while future development focuses on enhancements and increased capacity.

Support for Modbus devices on LonWorks Free Topology networks is currently available.

Support for Modbus devices on BACnet networks is currently available (MS/TP and IP).

Is a Babel Buster® easy to set up?

"Easy" is a relative term. If you are new to gateways, the answer is probably "no". But many customers who have used other gateways do tell us that ours are easier to set up than any other gateway they've used. All the drivers you need are included in the one low price. Gateways with Ethernet protocols include a web server with all configuration software contained within the gateway itself. Most other gateways have PC based tools which are available for free download on this web site.

I don't know anything about Modbus. Where do I start?