Nonvolatile memory system enabling nonvolatile data transfer during power on

Claim 1

A nonvolatile memory system including a plurality of unit memory cells arranged in a matrix array, each unit memory cell including a bistable circuit and first and second switching transistors, said bistable circuit having a pair of bistable points, at lease one pair of variable threshold field effect elements each having a first electrode connected to a corresponding bistable point, and first electrodes of said first and second transistors being connected to the bistable points respectively, said memory system further comprising: a plurality of pairs of digit lines, each pair being connected to corresponding second electrodes of the first and second switching transistors in each unit memory cell in the column direction of the memory matrix array; a plurality of word lines, each, connected in common to the gates of the first and second switching transistors in each unit memory cell in the row direction of the memory matrix array; a first decoder for selecting at least one pair from said plurality of pairs of digit lines; a second decoder for selecting at lease one of said plurality of word lines; a pair of data lines for transferring data to at least one pair of digit lines selected by the output of the first decoder; control signal generating means for supplying a control signal to the variable threshold field effect elements in each unit memory cell; first means for selecting at least one unit memory cell through said first and second decoders; second circuit means external to said unit memory cells for causing both bistable points in the selected cell or cells to be set to ground level through the digit lines; and third means for causing a readout signal from the control signal generating means to be supplied to each variable threshold field effect element after the bistable points are set to ground level.