| 摘要 |
PURPOSE:To prevent the illegal access of a memory by performing main gate open on the condition of all gates open. CONSTITUTION:Plural gates 2-4 and flip-flop(F/F) circuits 6-8 are provided at the preceding step of a main gate connected to a ROM. In this case, by inputting respective condition data such as address signals or data signals to the respective gates 2-4 in a prescribed order, the respective gates 2-4 are opened, and the respective F/F circuits 6-8 are set. When any condition data not matched with previously decided condition data are inputted, a gate 5 and an F/F circuit 9 close the F/F circuits 6-8. Then, on the condition that all the plural gates 2-5 are opened, the main gate is opened, and signals are outputted from the F/F circuit 8. |
