| 摘要 |
A nonvolatile memory system includes a memory array. The unit memory cell includes a bistable circuit having a pair of bistable output points and at least one pair of variable threshold field effect elements connected to the bistable points. The memory system further includes, decoders for selecting at least one unit cell, a pair of data lines to be connected to the digit lines of the selected unit cell or cells, a first means for driving the decoders to select at least one unit cell, a second means, external to the memory cells, for causing the bistable points in the selected memory cell or cells to be set to a ground reference level through the digit lines, and a third means for causing a read control signal from a corresponding control signal generator to be supplied to the variable threshold field effect elements so as to transfer data stored in the threshold field effect elements to the bistable points. The second means allows the bistable points to be set to the reference potential and any non-volatile memory cell can be read at any desired time during the "ON" state of the power supply source. Since the second means is external to the memory cells, a conventional memory cell array can be used without modification, and no great chip area is required in arranging such cells. During a read or write transfer between the bistable points and non-volatile memory cell sections it is possible to select individual unit cells or all cells at once.
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