Semiconductor device

A semiconductor device, comprising:

• a first arithmetic core;
• a second arithmetic core;
• a shared resource for shared use by the first arithmetic core and the second arithmetic core;
• a system bus through which signals are exchanged between the first and second arithmetic cores and the shared resource;
• a comparator which compares a first group of interface signals outputted from the first arithmetic core to the shared resource and a second group of interface signals outputted from the second arithmetic core to the shared resource and, when the first group of interface signals and the second group of interface signals do not agree, enables a first error signal;
• a selector which, in a lock-step mode, prevents the second group of interface signals from being outputted to the system bus and, in a split mode in which the first arithmetic core and the second arithmetic core operate differently, sends the second group of interface signals to the system bus;
• an access monitor which checks for a monitoring target signal included in the second group of interface signals outputted to the system bus via the selector and, when the monitoring target signal is outputted to the system bus, outputs a second error signal;
• and
• an error control unit which detects, based on the first error signal and the second error signal, an abnormal state of the first arithmetic core or the second arithmetic core or the selector and, based on the detected abnormal state, outputs an abnormal state processing request to a higher-order system, thereby requesting execution of processing to deal with the abnormal state,
• wherein, in the lock-step mode, the monitoring target signal has a predetermined value in a normal state, the predetermined value changing in an abnormal state caused when the selector fails.