Abstract: The present invention relates to a PROM writer which functions to compare the first check sum value of the first or reference data read out a master ROM with the check sum values of the second and subsequent data from the master ROM. The data read out of the master ROM is written into the plurality of the blank ROMs and the present invention prevents wrong data from being written into the blank ROMs based on a failure of a successful comparison between the first check sum value and the second and subsequent check sum values.

Abstract: There are disclosed a system for and a method of detecting a reverse packaging of a PROM capable of judging the packaging state of PROM having different impedances by adding an impedance switching circuit to the conventional socket. The method includes the steps of turning off the switch in the impedance switching circuit so that the socket receives a first voltage supplied from one of the impedances, storing the first voltage received by the socket, turning on the switch in the impedance switching circuit so that the socket receives a second voltage supplied from another impedance, storing the second voltage received by the socket, and judging that the PROM is normally packaged in the socket in case that the first voltage is equal to the second voltage and the PROM is reversely packaged in the socket in case that the first voltage is not equal to the second voltage.