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Old July 25th, 2018, 03:26 PM   #1
tim2
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CIP Symbolic vs CIP Generic messaging

Sorry if this is a beginner question, and I have looked at the manuals. Seems like a couple of tech notes would answer my question but I don't have access.

I think symbolic is to actually read or write variables while generic is for reading controller parameters, but not sure?
I've seen reference to symbolic being used for HMI to PLC, assuming this is because the HMI typically displays variables.

Question is what is the difference between the two types of MSG instructions (this is in a micro800).


Second question, if I am trying to message a couple of bits or bytes between two micro820 controllers, which would I use. the couple of bits are just used to handshake between two stations (station 1 ready to station 2, ...)

Third question, If I am trying to read data from a micro800 using a CompactLogix, which type of instruction do I use.
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Old July 25th, 2018, 09:37 PM   #2
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Symbolic means by a name such as a tag name. In contrast to using the Class, Instance, and Attribute numbers.

In CIP everything is referenced by numbers that refer to the Class type, which instance of the class, and the Attribute (or property). All tags belongs to a particular class and each has a unique instance number assigned to it. The attribute could refer to something such as the value or data type. Using Symbolic Addressing, the Message Router can cross reference the name to the class and instance ID.
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Old July 26th, 2018, 08:09 AM   #3
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Thank you.
So, if I'm reading that right the symbolic is just easier to configure?

So if I'm trying to message a couple of bits between two 820's just use the symbolic. Will get the same result just easier to configure?

If I am trying to read data from a micro800 using a CompactLogix, the Studio 5000 MSG instruction doesn't really have a symbolic option. In that software the MSG instruction is like the micro800 generic instruction and requires all the extra configuration, or can I just point it to a global variable in the 800?
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Old July 26th, 2018, 10:57 AM   #4
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For reading tags you generally want to use symbolic addressing because not all firmware supports reading tags by class and instance. Also a change in the program could cause a tag to be assigned a new instance number.


I wouldn't be able to offer much help on the Micro800 series because I have done very little with them.
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Old July 26th, 2018, 11:18 AM   #5
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If your wanting to read/write variable in both or multiple micro800 plc's I would differently use Modbus TCP. Very easy to setup and works perfectly!

Create a Modbus Table in one or both plc's and then use the "Msg_Modbus2" function block.
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Old July 26th, 2018, 11:26 AM   #6
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I have worked with a driver (and it is not yet finished) to communicate with Micro 820, using class3 connected messages.

I use symbolic addressing, it works well although Micro 800 has important limitations, it does not allow reading of several tags in a single request.

Also members of structures can't be read, just simple data types including String that for Micro800 is one more data type, instead for CLX a String is a type of structure.

I have not tried with class-attribute addressing
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Old July 26th, 2018, 12:20 PM   #7
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Quote:
Originally Posted by lfe View Post
it does not allow reading of several tags in a single request.
Modbus TCP allows reading of 125 tags at one time if they are in a seq address.
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Old July 26th, 2018, 12:21 PM   #8
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Thank you all.
Would love to use Modbus but hands are tied.
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Old July 28th, 2018, 05:08 AM   #9
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Quote:
Originally Posted by damica1 View Post
Modbus TCP allows reading of 125 tags at one time if they are in a seq address.
i think that Ethernet/IP can read consecutive members on an array tag from Micro800 with a single request but I didn't test it yet.
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