| 摘要 |
<p>PURPOSE:To obtain an EEPROM which can be switched from the reading or writing of quaternary data to the reading or writing of binary data, and vice versa, in accordance with control signals. CONSTITUTION:When a control signal, inputted to a control input terminal 109 is high against a selected memory cell 243-274, a program circuit 121 selects one from among four voltage values, for example, 22V, 20V, 18V, and 16V and applies the selected voltage across a selected bit lines 134-141 through a multiplexer. Then, the circuit 121 writes quaternary data in the selected memory cell 243-274. When the control signal inputted to the terminal 109 is low, the circuit 121 applies either one of two voltages, for example, 22V and 16V across the selected bit line 134-141 and writes binary data in the selected memory cell 243-274. At the time of reading out, either a quaternary sense circuit 2 or binary sense circuit 1 is selected in accordance with the control signal inputted to the terminal 109.</p> |
