| 摘要 |
PURPOSE:To hold the information even though an electric power supply is dropped or cut off and to attain large capacity with a small number of component TRs, by using two elements of nonvolatile semiconductor memory element having floating gates to a bistable circuit. CONSTITUTION:A bistable circuit consisting of insulated gate type field effect TR(IGFET)M1-M6 contains two nonvolatile semiconductor memory elements Ma1 and Ma2 having floating gates. Thus a nonvolatile RAM is obtained. The element Ma1, etc. having a floating gate 3 utilizes an F-N tunnel current phenomenon. The output information of the RAM can be written to the elements Ma1 and Ma2 by setting potentials of VCG, VS and X1 as earth potential to change VPP to 25V from 5V. The writing is carried out to the element Ma whose drain is connected to an output contact having its output state set at ''1''. Thus VT is reduced. While no writing is carried out to the element Ma whose drain is connected to an output contact having its output state of ''0''. Thus the VT has no change. In such a way, the output information is written to the element Ma. If a power supply is cut off under such conditions, the output information is already written to the element Ma and held semipermanently there. |
