A semiconductor device is provided which can quickly detect a malfunction of high priority modules by frequently checking a coupling state between the high priority modules and a communication bus.According to an embodiment, a host controller includes a module control circuit that performs data communication with a plurality of externally-provided modules through a communication bus, a coupling state check circuit which is coupled to the communication bus and which checks the presence or absence of a response from the modules, and selected from the modules based on information of a check list, and a control circuit that selectively causes the module control circuit and the coupling state check circuit to operate.