MVI56 module to communicate with Control Logix processor

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Thread Starter

Yogi

We are trying to configure MVI56 MCM module. It is installed in a Control Logix chassis. This MCM module is connected to two slaves. What i want to know is how to write data to those two slaves. How to identify them as 1 and 2???
 
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Steve Myres, PE

The slaves need to know their own addresses so that they can recognize comms addressed to them. There will be some hardware (dip switches or jumpers or keypad, etc.) or software (RS232 port) means included in the slave to set the address.
 
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Michel A. Levesque, eng.

I assume that you cut/paste the standard CLX ladder code available from Prosoft for communicating with the MVI56.
This code sets up the various data registers in the CLX processor for the MVI56 card. The code uses MOV and CPO instructions to exchange data from the CLX data variables to the MVI56 card variables.

The user-defined variables that are set up allows you to configure Modbus messages to slaves (up to 100 messages are initially configured). Basically you write the slave address and the data addresse along with the message type in memory variables, the code and the MVI56 card take care of the rest. Very clean and relatively painless setup.
HOWEVER, the communications bandwidth between the MVI56 and the CLX are just massive. I suggest you install the MVI56 card in the same physical rack as the processor.
 
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In our MVI56-MCM, you define commands as a Modbus Master in the MCM.P2Cmd Controller Tags. The Device parameter in each command determines what slave ID the command will be issued to. Each Modbus slave must be assigned a unique ID on a multi-drop network.

Please feel free to contact me offline at [email protected], or call at 661-716-5100
 
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