METHOD AND DEVICE FOR TESTING MICROCODE

PURPOSE:To shorten a time necessary for a microcode test, to reduce expenditures, and to improve reliability by providing a parity checking part, etc., which execute parity checks every microcode, and detect errors. CONSTITUTION:The code for the parity check is added to the microcode stored into a ROM 1, and information stored into an address designated by an address decoder 6 is outputted to a parity checking part 2. The part 2 checks the microcode through exclusive logical sum gates E1 to En, a result is outputted from the gate En to an error holding part 3, when the result is normal, the part 3 outputs data at '1', when the error exists, data at '0' are outputted to an arithmetic operation runaway generating part 4. When the data from the part 3 is at '0', since the part 4 does not output a timing state T1 to a decoder 6, the part 4 cannot be timed, the operation of an arithmetic part runs out of control, and the error is detected. Thus the test time of the microcode is shortened, the expenditures are reduced, and the reliability can be improved.