A solid state memory employs a plurality of memory cells each capable of storing either of two different binary values. The memory cells require periodic application of a refresh pulse to the memory cell to, without rewriting, enhance at least one of the two different binary values which the memory cells can store, in order to prevent loss of that binary value over a period of time. The reliability of the memory is improved by supplying a refresh signal which includes a plurality of refresh pulses in each memory cycle.

A refresh counter which uses existing address buffers and is implemented with refresh address storage and decoders. The address buffers act to multiplex the refresh address storage outputs as inverted outputs when properly enabled. When all lower order bits are true at a particular unit of the refresh counter and a transfer clock signal occurs, the outputs of the buffer are transferred to the refresh storage where the buffer multiplexes them when enabled. The clocking scheme is structured to enable only at the end of a refresh cycle. In this manner, the counter is incremented at the end of each refresh cycle.

Memory cells in a random access memory system are addressed through associated X and Y address lines. Each memory cell is operable as a static memory device to represent "1" binary data in response to a first control potential applied to the associated X address line and a first data input potential applied to the associated Y address line and further operable as a nonstatic memory device to represent "0" binary data in response to the first control potential applied to the X address line and to a second data input potential applied to the Y address line. Means are provided to refresh the stored "0" binary data by simultaneously applying a second control potential lower than the first control potential to all of the X address lines at periodic intervals and simultaneously therewith applying the second data input potential to all of the Y address lines.

A semiconductor memory is provided with means for refreshing the memory. Interrupt requests generated by the memory initiate refreshing cycles which are uniformly distributed during periods of normal operation of the memory, each cycle for a row of the memory. In a first time interval, an interrupt request has a low priority level and does not necessarily interrupt the operation of the computer. If the low priority interrupt request is not responded to, a second interrupt request with a high priority level is generated; this high priority level second interrupt request is responded to without fail.

This invention involves a memory cell of, for example, the metal-oxide-semiconductor (MOS) capacitor type, which is accessed for reading and writing by means of an access network connected to the memory cell through a gating transistor, and which is provided with an independent refresh network for maintaining the memory state of the cell in the absence of an access writing signal. The refresh network includes a pair of IGFET (Insulated Gate Field-Effect Transistors) transistors connected between the MOS capacitor and an AC refresh line which is completely independent of the electrical access network. Either a "full" or "empty" capacitor memory state, binary digital 1 or 0, respectively, is maintained without the need for interrupting the reading and writing of the MOS capacitor through the gating transistor.