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.