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About sban346

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    Hi, I am New!

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  1. Reading and Writing I/O tags in PLC

    So, for explicit messaging, we do not use classes and instances to access the tag information? Since CIP uses the concept of objects and classes for communicating between CIP devices, I was hoping to there would be a class that is used to access these tags.
  2. I am reading and writing to I/O tags in Logix5571 using python. While dissecting using Wireshark, I could see that the Symbol Class(0x6b) is being accessed with Service Codes 0x4c and 0x4d. I am confused about the following: 1. Is this the convention in which I/O tags are accessed, as in using the Symbol Class? Is it not Assembly Class? I have read that while doing implicit messaging, Assembly Class is used to access the I/O tags, is it different for the explicit messaging? 2. The services 0x4c and 0x4d are specific to Symbol Class?  3. How to know what are the instances and attributes present in this class?