| 摘要 |
A D/A converter converts input "n" bit digital data into discrete analog data by assigning each of the voltage values V0-V2n-1 to each "n" bit digital data. A non-volatile memory capable of write and readout of analog data is used as a memory. The memory stores each analog data, which is represented by one of the voltage values V0-V2n-1 corresponding to each "n" bit digital data, into a memory cell. The analog data readout from the memory is supplied to an A/D converter to be converted into the original "n" bit digital data. Thus, digital data represented by a plural number of bits is stored in a single memory cell, and memory capacity can be increased with a simple structure. The memory is divided into two areas, that is, a read/write area which allows both reading and writing and a write restricted area to which writing is restricted. A write restriction circuit prohibits writing of analog data to the write restricted area. In this structure, a single memory functions as both a ROM and RAM.
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