In industrial automation, there are situations where IO instruments are located very far away from the panel and it cannot be interfaced with the local PLC due to the distance involved.
For this reason, remote IO modules are available which just communicate the data of these IOs with the main PLC. This makes communication easier as well as provides flexibility for instrument engineers to place the instrument anywhere required.
Remote IO Adapter Module
The communication between the remote adapter and the main PLC is mostly done through Ethernet, which is the fastest and the most efficient mode of communication.
Such remote IO modules are available in many PLC brands. Out of that, Schneider Electric is such a brand and in that, a BMXCRA or BMECRA module is available for use. In this post, we will see the concept of CRA modules in Schneider PLC.
CRA Module in Schneider PLC
CRA is a remote IO adapter module in the Schneider PLC automation range. It does not have any CPU for writing logic; it is just a data communicator. It takes IO values and updates them to the main CPU continuously. The module works on Ethernet IP protocol. It has three LAN ports for working.
Apart from standard IO values, the module also provides various types of diagnostics for troubleshooting. This helps the programmers in writing the logic more flexibly. For example, you have three IO modules at a very fast distance from the CPU. Then, just configure these three modules in the CRA module in the software; and the CRA will then use it for data communication with the CPU.
Module Configuration
The module has two rotary switches on it. They define the ID of the module. For example, there are 4 CRA modules used in the system. All four are located at far distances from each other. Then, each module must be given a separate identity so that it can be distinguished easily by the CPU logic.
Also, the module IP is set in the CPU program. There is no configuration in the CRA module. Just properly configure the IP addresses in the PLC logic for the CRA modules, set the ID by rotary switches, and your CRA modules will start functioning accordingly.
The module has four LEDs in it for troubleshooting – Run, IO, Module status, and Network status. Read the catalog of the module in detail for proper description.
Schneider PLC Communication Module
The module is supported only in M580 and Quantum range of Schneider PLC’s. One interesting thing about this module is that it has a large number of communication services like SNMP agent, SNTP client, FDR client, FTP client, TFTP client, DHCP client, CIP explicit messages, and Quality of Service. All these are a part of cybersecurity features and help in protecting the module from cyberattacks.
The CRA modules are completely redundant. It depends on how you network the system. The level of redundancy depends on how you cable the wires and how you decide the topology. Based on that, you can safely operate the logic without the fear of IO data loss.
For example, you have two CRA modules and want IO redundancy. Based on the topology it supports, you can design the network in such a way that if one LAN port of the first CRA module fails, then you can take data via the second LAN port to the second CRA module and then to the main PLC. Various routing options are available.
In this way, we saw the concept of the CRA module in Schneider PLC.
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