Knowledge Base / Rockwell In-chassis / ControlLogix / MVI56 Series

How does the MVI56MCM module work in a Redundant Control Logix Setup?

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Since all I/O modules in a redundant ControlLogix application must reside in the remote rack, the ProSoft MVI56MCMR(r) modules must also reside in those same remote I/O racks. As far as the ControlLogix processor is concerned, all MVI56 modules are just an I/O module. For the MVI56-MCM module, the ControlLogix processor will see the module as an I/O module with 250 int words (500 bytes) of input data, and 248 int words (496 bytes) of output data. It is the use of the input/output images that allows the ladder logic to transfer data to the MVI56 module. Because of the large I/O size of the MVI56MCM you may often run into issues scheduling this module in a remote I/O rack. For this reason ProSoft recommends using the MVI56MCMR module when placing the module in a remote I/O rack. The MVI56-MCMR module has a smaller I/O size of 42 int words (84 bytes) of both input and output data. This eases the traffic on a ControlNetnetwork, and will allow the module to easily be scheduled without having to increase the nut, RPI, or changing other ControlNet parameters. For any remote rack application, reduandant processors or just remote racks, it is always a good idea to use the MVI56-MCMR module to ease the load of a ControlNet or EtherNet I/P network.

Related Keywords:

MVI56MCM MVI56MCMR all MVI56 modules