For any details of the system requirements, refer to the chapter System Requirements.
The function block supports cross checking with another instance of the function block running on a library-compatible controller, or by using an M221 Logic Controller with the cross checking logic implemented in EcoStruxure Machine Expert - Basic. For details refer to the user guide Diagnostic Coverage for M221 - Application Guide.
The following diagram depicts the checks performed by the function block. Cross checking between two controllers/function blocks is done using a test value generated by a pseudo-random number generator (Congruential generator) and digit sum of this number. Both numbers must be transferred at the same time to a diagnostic coverage function running in another controller. Any supported communication interface can be used to transfer data between the controllers.
Internal structure of the DiagnosticCoverage_2 FB
Cross check between two controllers
