In a processor or the like including a reconfigurable (RC) circuit, the RC circuit is used to form a test circuit to test a core, a cache memory, or the like, and then part of the RC circuit is used as an auxiliary cache memory. When a memory can store data after stop of power supply, a startup routine program (SRP) of the processor can be stored therein. For example, after the test, an SRP is loaded to a memory in the RC circuit from an external ROM or the like, and when power is resupplied to the processor, a startup operation is performed using the loaded SRP. When the processor is in a normal operation state, this memory is used as an auxiliary cache memory and the SRP is overwritten. The SRP is loaded to the memory again at the end of use of the processor.