Interfacing a Gateway RS232 DLMS-MODBUS in Modbus

[Sergio Bertana]

I receive a request that can be interesting to other customers so i post it.

I am working with a Gateway RS232 DLMS-MODBUS, trying to connect with it in Modbus TCP, but I can’t.

I have change the IP address and I can see the webpage of the device, but I can’t download data via Modbus. I am reading 2 words in the 40001 address. All I have is the error message: Data address error.

Please help me. What I can do to download data via Modbus TCP ? The device code is:  MPS046B100

[Sergio Bertana]

Just to clarify, the Gateway RS232 DLMS-MODBUS is a product developped by Marcom (See the WebSite). It is based on our SlimLine ARM7 IEC61131-3 CPU module our code MPS046B100.

The software is completely developped by Marcom and we do not have any information on it, anyway the modbus TCP support is native in the SlimLine product, so I can inform how the protocol itself works, but I haven’t any informations about the Modbus registers. The Modbus protocol supports codes 0x01, 0x02, 0x03, 0x04, 0x05 0x06 and 0x10 and address starting at 40000, there is also an address’s alias at 20000 (See IEC 61131-3 Programming manual abstract).

I don’t know what program do you use to read the modbus data,  I suppose that the Data address error message is returned by the program you use. In that case it could be the register address 40000 that is not managed by some SCADA programs, so I suggest to use its alias 20000.

[Sergio Bertana]

In the manual abstract are reported some Modbus frames, to use them, and so to try if the modbus communication works properly you can use our Toolly program. Using Toolly as a terminal emulation it’s possible to send data to a serial connection even to a TCP/IP connection. So assuming that the SlimLine is connected to the PC by Ethernet you can try Modbus communication (See screenshot).

[Anonimo]

Hello Bertaser, thanks for your answer. I have installed your software (Toolly) but the device don’t anwser the message. I also tried to use the address 20000, but the program i use tell me that this is an incorrect address.

I’m using several programs and devices to connect, the Main device is a Siemens PLC S7 1214. But i also tried with a modbus simultator from the computer (This one). Maybe the Marcom people can tell me more about this issue. Thanks.

[Sergio Bertana]

It could be that someone has disabled the Modbus access to the device or he has changed the TCP port from the default 502 to another. Just to know if the TCP port 502 is still on waiting connection you can refer to the messages that appear in the Toolly status window when the connection starts (Refer to screenshot).

If an Error open message appears this means that the Modbus could be disabled (In this case only Marcom can help you). If the problem is a different TCP port you have to refer to the web page (See screenshot).

I’ve tested with the Radzio program on a SlimLine CPU module and it works correctly, I have read 10 Holding registers starting from address 40000 (See screenshot).

[Luca Marani]

On the gateway DLMS manual there is written clearly the address MODBUS to read. If You findi 40001, it means address 40001 in holding register area and not address 1 in holding register area.

[Autore]

Post