4/4/2010 3:31 PM | |
Posts: 18 Rating: (0) |
Came to knowsome sort of Modbus TCP solutionis coming upin a month's time. Can't Wait!!! |
4/6/2010 3:26 PM | |
Posts: 21 Rating: (4) |
Hi, The send/recv telegrams must follow a specific structure. I have established Modbus TCP comms from a 1200 to a PAC 3200 power meter. The key is structuring the telegram headers for send and receive. The link below describes these structures: http://www.rtaautomation.com/modbustcp/#11 I send the following: Transaction ID = 0 Protocol ID = 0 Field Length = 6 Unit ID = 1 Function Code = 3 Start Register = 1 Number of Registers = 30 The data to be sent is 6 bytes long (Unit ID, Function Code, Start Register, Number of Registers). This structure will read back 15 real numbers (30 word length modbus regiaters) starting at address 1 from slave device 1. The response (reply telegram)is: Transaction ID = 0 Protocol ID = 0 Length = Unit ID = 1 Function Code = 3 Modbus Data Length = 30 The registers after this contain the modbus values from the slave device (15 reals). The problem that I had here was that the reply header is 9 bytes long. To maintain symbolic addressing for use further int he user program, I had to move each real number from say DBD9 to another DB address of DBD10. DBD10 conatins the symbolic name for that value. Without doing this you may see values coming in, but they will only be valid every 6 polls or so. If everything looks like its working but the values are nonsense, try monitoring the raw data and I think you will see the data is there but just needs moving into the correct byte order. Hope this helps? |
5/12/2010 10:47 AM | |
Joined: 5/28/2008 Last visit: 9/11/2024 Posts: 1343 Rating: (141)
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here it is: Data Communication via Modbus/TCP with S7-1200 (CE-X22) |
This contribution was helpful to2 thankful Users |
12/9/2010 12:18 PM | |
Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (152) |
Dear Slack, I have sent you a PM. Or anybody who knows how to implement a simple Modbus TCP/IP server, please help. |
3/9/2011 8:36 PM | |
Posts: 5 Rating: (1) |
What do you need the Server or the Client? Send me an email and i will give it to you. Too large for the Forum. |
3/9/2011 8:39 PM | |
Posts: 5 Rating: (1) |
Here is a link to both the Server and Client, these are not supported by Siemens yet but will get the job done. ftp://RadfGA:ChU5eF!ereSa@ftp_server.webautomation.info Let me know how it works for you. |
This contribution was helpful to2 thankful Users |
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