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Choosing the Right Modbus RTU Module for S7-1200

Created by: karl_smith77 at: 8/15/2024 9:50 AM (4 Replies)

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8/15/2024 9:50 AM	Rate (0)
karl_smith77 Joined: 7/4/2024 Last visit: 7/14/2025 Posts: 53 Rating: (0)	Hello everyone, I'm setting up a Modbus RTU communication via RS485 for my SIMATIC S7-1200 PLC " reference:6ES7 214-1AG40-0XB0". I'm trying to decide between the following four communication modules, and I would like to know which one would be the most suitable for my needs according to my PLC: 6AG1241-1CH30-5XB1 6AG1241-1CH31-4XB0 6AG1241-1CH32-2XB0 6AG1241-1CH32-4XB0 If anyone can point out the main differences between these modules and recommend the most appropriate one for Modbus RTU communication via RS485 with my PLC, I would greatly appreciate it. Thank you in advance for your advice!

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8/15/2024 12:45 PM	Rate (1)
Towome Platinum Expert Joined: 7/9/2015 Last visit: 1/15/2026 Posts: 4496 Rating: (644)	Hi, why do you want a CM1241 as SIPLUS because you use a standard PLC S7-1200. I think 6ES7241-1CH32-0XB0 would be great. Check this: How do you establish a MODBUS-RTU communication with STEP 7 (TIA Portal) for the SIMATIC S7-1200? Regards, Towome
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8/15/2024 5:44 PM	Rate (0)
karl_smith77 Joined: 7/4/2024 Last visit: 7/14/2025 Posts: 53 Rating: (0)	Hi Towome, I need the module to connect my PLC to a VFD, which requires Modbus RTU communication via the RS485 interface. Thanks ! Karl

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8/16/2024 5:42 AM	Rate (0)
Towome Platinum Expert Joined: 7/9/2015 Last visit: 1/15/2026 Posts: 4496 Rating: (644)	Hi, if you are not sure which Siemens product is best suited to your application, you can contact the Siemens presales technical support team! Regards, Towome
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8/16/2024 7:52 AM	Rate (1)
qwazee Platinum Member Joined: 3/30/2020 Last visit: 12/11/2025 Posts: 5656 Rating: (1083)	karl_smith77 Hi Towome, I need the module to connect my PLC to a VFD, which requires Modbus RTU communication via the RS485 interface. Thanks ! Karl using a communication board instead of a communication module would be best for your application, in my opinion. The CB1241 (6ES7 241-1CH30-1XB0) is an add-on board that pushes directly into the CPU. It is less expensive and has terminals on the board instead of the DB9 connector. Also included to the board is the terminating resistor. Search for the part in the S7-1200 system manual. Look at the specifications and the installation notes. Either the CM1241 or the CB1241 will work to transmit Modbus RTU over the RS485 link.
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