I have to connect ABB DCS with Emeson DCS. We choose Modbus RTU for this communication. But the problem is now two DCS hardware's modules are set as Master. It can not change. Is there any equipment between two Modbus RTU Master can help them for communication?

Otherwise, ABB module is only use Modbus RTU, but Emerson can use Modbus RTU or TCP. So, can I have solution to connect Modbus RTU with Modbus TCP with both side is master?

Thanks for your help!

 

Hi,

Set up a gateway with two Modbus RTU slaves,you can do this with a FieldServer gateway.

Thanks,
Richard

 

You could use our Omnii-Comm product http://www.miille.com/din266-p00.pdf for this application. Conceptually, you would define a block of Modbus Holding Registers that can be written to or read from by each Modbus Master at any time. You may contact me off list if you need additional information.

Jerry Miille
713-472-6272 (work)
713-472-0318 (fax)

 

The ICC XLTR-1000 has two RS-485 ports, each of which can be configured with Modbus RTU slave drivers (thereby allowing two master devices to exchange information, with the gateway acting as an intermediary).
http://www.iccdesigns.com/products/millennium/xltr-1000.html

If you are looking to convert between Modbus/TCP and RTU, then the ETH-1000 is from the same product family, but replaces one of the RS-485 ports with an Ethernet port. One of the drivers that can be configured on the Ethernet port is Modbus/TCP server, so again you can exchange information between two masters through the gateway (in this case, one RTU master and one TCP master).
http://www.iccdesigns.com/products/millennium/eth-1000.html

Regards,
Darrin

 

I knew there would be many answers

What you must do is buy one of the above devices, then have one of your Master 'write' the data share to this device (you can also just buy a small Modbus PLC with 2 serial ports).

Then the second master reads from the shared slave. Just be careful how the second Master 'validates' that the data is valid. For example, if the link between first master and device fails, the data will go stale and might fool the second master.

All of the devices above should offer a solution to this directly (they might include a 'health-status register', or even mimic a dead slave with time-outs - check with the vendor as to how this is done.

If you use a small PLC, you'll need to design your own scheme. For example, have the second master write a value 1 to some register, and have the first master reset it to 0 any time it updates the PLC. Thus, if the register remains the value 1, then the first master is no longer updating the data.

 

Thanks for all,

Last time I think it is only a way using PLC that is the same Lynn August Linse’s way. But it is more trouble in installation and program.
Now I can see more ways able to do as you introduced. I like the way of Darrin, and I think I will following this way. It is an easy way.

And dear Darrin,
If you don’t mind, please give me your email address, I think I need more your help when I have trouble in the connection.
Thanks for all your replies again!
Best regards,

Jianjian,
email: [email protected]

 

Hello,

I see there are several replies already! Let me add this: Comtrol Corporation makes a Device called "Devicemaster UP" that can easily connect 2 Modbus masters (or 2 modbus slaves) among other unusual capabilities within Modbus. You would only need one gateway, but with 2 ports on that gateway. Each port is configured (on the Modbus side) to be a Master. The other side of the communication is a TCP socket. You aim the TCP socket at one port to the port next to it, and hence there is kind of "two internal slaves tied to each other that are transparent to your two external masters." Hence you can tie a Master to another Master with one piece of hardware. Here is a whitepaper they released recently:

http://www.comtrol.com/elements/uploads/fckeditor/file/DMUP_ModbusControllertoController_LT1483A.pdf

(Example 1.13 on page 4 fits your situation.)

You could definitely use a PLC with some of the tips that the others mentioned, but a gateway should be quite a bit cheaper/quicker