Abstract: A control system has a first module that includes a memory and diagnostic logic. The diagnostic logic periodically tests at least selected locations in the memory and, in connection with such testing, reads data from those locations and writes that data back to the locations. A second module is coupled to the first module such that the written back data is transferred to the second module, as well as to the memory of the first. Mapping or other conversion logic can translate addresses or other data identifiers, as necessary, to insure that the transferred data is properly identified upon its receipt by the second module.

Abstract: A computer is connected to redundant network switches by primary and secondary connections, respectively. Test messages are sent across each connection to the attached switches. A break in a connection, or a faulty connection, is detected upon a failed response to one of the test messages. In response to this failure, traffic is routed across the remaining good connection. To facilitate fast protocol rerouting, a test message is sent across the now active connection bound for the switch connected to the failed connection. This message therefor traverses both switches causing each to learn the new routing. Rerouting is therefor accomplished quickly.