| 摘要 |
PURPOSE:To surely protect data while effectively using the memory space of semiconductor memory. CONSTITUTION:A logical operation circuit 20 is provided in the semiconductor memory 1, and a logical operation circuit 25 which executes the same operation as that of the logical operation circuit 20 is provided at an external operation circuit part 2 connected to the semiconductor memory 1. Those logical operation circuits 20, 25 execute a specific logical operation repeatedly, and computed result data are compared with each other sequentially by a comparator 23. While coincidence between them is obtained, a gate circuit 18 passes storage data, however, when the comparator 23 outputs a noncoincidence signal, hereinafter, the storage data is judged, and data with erroneous content is outputted. Therefore, it is possible to prevent normal data from being read out even if a different external logical operation circuit is connected to the semiconductor memory by a third party, which enables the logical operation circuit 25 to be used as a key. |
