PURPOSE: To minimize the occupied area of a circuit for check by introducing a serial data input after a shift register is preset by a shift register for preset.

CONSTITUTION: A serial data input is serial/parallel converted by a shift register 6. An accumulator 7 inputs a parallel output of the shift register 6 and fetches a data output of an RAM9 and checks the serial data input by comparing both data. In using the check device, a data is preset to the shift register 6 for serial- parallel conversion by the RAM9 and the shift register 8 for preset in the test mode at first. Then the mode is changed over into the normal mode and the serial data is inputted to the shift register 6 through a serial data input terminal 3.