Checker Core_0s operates in lock step mode with Main Core_0, executing exactly the same instructions as Main Core_0. Thus, Checker Core_0s checks to insure that Main Core_0 is executing correctly. RCCU (Redundancy control checker unit) continuously monitor lock step and if it founds inconsistency it reports this fault to FCCU. In FCCU you can decide whenever you like to trigger interrupt, reset or signal it to outside world. The Checker core and RCCU are disabled in debug mode and it runs in normal mode (no need to enable it manually).