1. A processing apparatus comprising: a first register file; a second register file configured to hold a part of data held in the first register file; an operation unit configured to perform an operation using data in the second register file, and to output an operation result as output data; an instruction unit configured to issue a write instruction to write the output data and an error detection code for detection of an error in the output data to both the first register file and the second register file, a first occurrence instruction to generate a simulated fault in the first register file, and a second occurrence instruction to generate a simulated fault in the second register file; a first control unit configured to issue a first generation instruction upon receipt of the write instruction and the first occurrence instruction; a first generation unit configured to receive object data that is input to the first generation unit, to generate first simulated fault data according to the object upon receipt of the first generation instruction, to output the first simulated fault data to the first register file upon generation of the first simulated fault data, and to output the object data to the first register file in absence of the first generation instruction; a second control unit configured to issue a second generation instruction upon receipt of the write instruction and the second occurrence instruction; and a second generation unit configured to receive the output data and the error detection code, to generate second simulated fault data according to the received output data and the received error detection code upon receipt of the second generation instruction, to output the second simulated fault data to the first generation unit as the object data and to the second register file upon generation of the second simulated fault data, and to output the received output data and the received error detection code to the first generation unit as the object data and to the second register file in absence of the second generation instruction.