You normally use such a scheme to pass data from the more critical to the less critical system. For example in nuclear power plants (that's where I know this sc

You normally use such a scheme to pass data from the more critical to the less critical system. For example in nuclear power plants (that's where I know this scheme from) your low-safety systems can use data acquired by a highly safety relevant system (e.g. to display the pressure, temperature and power generation of the reactor core without being able to influence the safety systems that primarily acquired the values).