Patent ID: 7239563

Claim:
A semiconductor device for outputting data read from a read only storage device, comprising: a plurality of read only storage devices, each read only storage device including memory cells; a plurality of selecting signal lines for transmitting selecting signals to the plurality of read only storage devices, each selecting signal line being connected to a corresponding one of the plurality of read storage devices, and each selecting signal indicating one of the plurality of read only storage devices storing data to be read; an address signal line for transmitting an address signal to the plurality of said read only storage devices, said address signal indicating an address of memory cells storing data to be read; and a switching device to which the selecting signals and the address signal are inputted, wherein said switching device comprise; an address storage circuit for storing address information of a defective memory cell of one of the plurality of read only storage devices and for detecting whether or not memory cells storing data selected by a selecting signal and an address signal include a defective memory cell; a data storage circuit for storing replacement data for memory cells including a defective memory cell, and outputting said replacement data in response to the detection of a defective memory cell by the address storage circuit; and a switching circuit for inputting data outputted from memory cells of one of the plurality of the read only storage devices which is selected by a selecting signal and an address signal and replacement data outputted from the data storage circuit and outputting data outputted from one of the plurality of the read only storage devices which is not stored in memory cell including a defective memory cell and replacement data from said data storage circuit instead of data outputted from one of the plurality of read only storage devices which is stored in memory cells including a defective memory cell.