I have an application where one ControlLogix needs to read data from another ControlLogix. The second PLC is part of a validated pharma process and it needs to be possible to guarantee that the first PLC can only read and never write data to the second PLC. I have seen so called “Data Diode” switches that understand the Ethernet/IP protocol and enforce the one way data path buy they are very expensive. I’m wondering if there are any less expensive solutions that will achieve the same goal.