How to Use the MESSAGE Instruction to Read Modbus Registers in AB CompactLogix Controllers

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• 18-02-2025
• Ones_Zeros

I never expected that integrating Modbus addresses into a PLC could be so challenging. The complexities arise largely due to Group Schneider's "Solaia" patent dispute, which makes utilizing Modbus with Rockwell products quite tricky. However, let's focus on the task at hand: the 1769-SM2 module. While it might seem daunting, it's actually relatively straightforward to set up. By consulting the user manual and keeping in mind that this module is intended for polling a select few Holding Registers from AC drives, you'll be able to successfully implement it.

• 18-02-2025
• Ken Roach

Ken Roach pointed out that the challenges of using Modbus with Rockwell products can be attributed to the "Solaia" patent dispute involving Group Schneider. It's a situation that many in the industry remember well. While this topic veers off course, I'm intrigued—could you elaborate on the details?

• 19-02-2025
• ASF

You can find extensive information by searching for "Solaia 318 OPC Rockwell Schneider" online. To summarize, Schneider Electric transferred a patent related to OPC-like technology to a "patent troll" law firm. As aptly stated by the OPC Foundation, "The '318 patent is as relevant to OPC as a recipe for gumbo." This law firm skillfully employed litigation against prominent companies utilizing OPC in conjunction with Rockwell products, pressuring them into settlements to acquire "licenses" for the technology. As a result, those companies were motivated to file lawsuits against Rockwell Automation to recover their financial losses. After years of legal battles, incurring millions in attorney fees, a court finally determined that the patent was unenforceable. The core issue of mistrust towards Schneider arises from a key revelation during the final court proceedings: the judge discovered that Schneider had sold the patent to Solaia for just one dollar, with a clear agreement to target only Rockwell customers and not Schneider's own clientele. This has led Rockwell to question Schneider’s intentions, especially concerning Modbus, a technology to which Rockwell holds a significantly stronger claim than they ever did for OPC. There is also concern regarding their agreements with Prosoft for developing Modbus products for legacy PLC/SLC systems, specifically excluding support for MicroLogix and SLC. Ultimately, Rockwell Automation harbors doubts about Schneider Electric, and I share those concerns. If you’re looking for trustworthy insights into the ongoing dynamics between these companies, staying informed is essential.

• 19-02-2025
• Ken Roach

Hello everyone, I'm revisiting a previous inquiry and would greatly appreciate your insights on hardware options to interface with an existing Modbus RTU controller. To recap, I have an Allen-Bradley 1769-SM2 Modbus RTU card that was configured before my tenure in the department. Its primary function is to read several Modbus registers from a Centurion controller. At the time of setup, there were message statements established to retrieve a range of registers from the Modbus controller, along with a custom Add-On Instruction designed to interpret those registers. Now, as I attempt to read additional registers from this controller and troubleshoot communication challenges, the process appears to be more complicated than necessary. I suspect this may stem from my difficulty in grasping the message read instruction and ensuring I'm connecting to the correct Modbus node on our RS-485 daisy chain, which connects to the same 1769-SM2 card. If anyone could share resources or links to help me better understand the message read instruction and the process of reading Modbus RTU registers into a CompactLogix 1769-SM2 card, I would be incredibly grateful. In prior projects, I successfully accessed these Modbus registers using serial RS-232 to Ethernet device converters into our SCADA software. However, this current data needs to be integrated into the PLC. I came across a device from Red Lion that facilitates the reading of five Modbus protocols simultaneously for the controller, but it comes with a hefty price tag of $1,000 each. Here’s a link to the Modbus controller I'm trying to access: Centurion-C4. Are there any more affordable hardware alternatives available that can achieve this? Thank you for your assistance!

• 19-02-2025
• Ones_Zeros

Explore the possibilities of using a Weintek Controller as an effective solution for converting Modbus RTU to Modbus TCP. By utilizing devices like this, you can seamlessly transform Modbus RTU data into the more versatile Modbus TCP protocol, enhancing your data communication capabilities. For more information on this technology, visit [ADF Web's Modbus Converter](http://www.adfweb.com/home/products/modbus_TCP_RTU.asp?frompg=nav3_8&loc_phy=9022672&k001=e&en-k1=modbus%20rtu%20to%20modbus%20tcp&d=c&g=18226497969&pos=1t3&gclid=EAIaIQobChMI_J2-y6-A2wIVAylpCh0Rzg2aEAAYAyAAEgJF1fD_BwE) for insights into innovative solutions that address your Modbus conversion needs. Enhance your industrial automation with integrated systems today!

• 19-02-2025
• damica1

User Ones_Zeros recently shared an interesting discovery: a device from Red Lion that can read five Modbus protocols concurrently to a controller. However, the price tag is quite steep at $1,000 each. You can find the Modbus controller I’m attempting to access for register data here: Centurion-C4. Is there any more affordable hardware available for this purpose? Thank you! To expand on this, any Red Lion HMI can accomplish this task, including the budget-friendly G304K2, which is priced around $400. I've successfully executed complex protocol conversions using this compact touchscreen. However, for a more robust solution, you might consider their newer CR1000 series, which costs about the same. If your project requires an HMI, selecting the right size will allow you to utilize it for both HMI functions and protocol conversion seamlessly.

• 19-02-2025
• OkiePC