Data storing apparatus having a memory capable of storing analog data

• US 5,689,453 A
• Filed: 06/22/1995
• Issued: 11/18/1997
• Est. Priority Date: 06/24/1994
• Status: Expired due to Fees

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Tsukagoshi, Masaaki
• Primary Examiner(s): Dinh, Son T.
• Application Number:
  US08/493,621
• Time in Patent Office: 880 Days
• Field of Search: 365/45, 365/195
• US Class Current: 365/45
• CPC Class Codes: G11C 27/005 with non-volatile charge storage, e.g. on floating gate or MNOS

Abstract

A D/A converter converts input "n" bit digital data into discrete analog data by assigning each of the voltage values V₀ -V₂.spsb.n_-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 -V₂.spsb.n_--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.

Claims

1. A data storing apparatus having a memory capable of writing and reading out analog data, comprising:

a D/A converter for converting digital data represented by a predetermined number of bits into discrete analog data;

a memory divided into a read/write area and a write restricted area, wherein the analog data is stored in at least one of the read/write area and the write restricted area;

an A/D converter for converting said analog data read out from the memory back to digital data represented by said predetermined number of bits; and

a write restriction circuit restricting the writing of said analog data into the write restricted area in the memory and controlling at least one of size and location of the write restricted area.

2. The data storing apparatus according to claim 1, wherein said memory is a non-volatile memory, which is capable of storing analog data by controlling the amount of electrical charge applied to each of a plurality of floating gates, thereby functioning as both read only memory and read/write memory.

3. The data storing apparatus according to claim 1, wherein said D/A converter creates analog data by dividing an entire voltage by a number based on the predetermined number of bits to produce discrete voltage values and by assigning each of the voltage values to each digital data represented by said predetermined number of bits.

4. The data storing apparatus according to claim 2, wherein said D/A converter creates analog data by dividing an entire voltage by a number based on the predetermined number of bits to produce discrete voltage values and by assigning each of the voltage values to each digital data represented by said predetermined number of bits.

5. A data storing apparatus having a memory capable of write and readout of analog data, comprising:

a first A/D converter for converting analog data into digital data;

a data compressor for compressing the digital data from the first A/D converter to generate compressed digital data represented by a predetermined number of bits;

a first D/A converter for converting the compressed digital data into discrete analog data;

a memory divided into a read/write area and a write restricted area, wherein the analog data is stored in at least one of the read/write area and the write restricted area;

a second A/D converter for converting the analog data read out from the memory back to the compressed digital data represented by the predetermined number of bits;

a decompressor for decompressing the compressed digital data; and

a second D/A converter for converting the decompressed digital data into analog data; and

a write restriction circuit restricting the writing of said analog data into the write restricted area in the memory and controlling at least one of size and location of the write restricted area.

6. The data storing apparatus according to claim 5, wherein said memory is a non-volatile memory which is capable of storing analog data by controlling the amount of electrical charge applied to each of a plurality of floating gates, thereby functioning as both a read only memory and read/write memory.

7. The data storing apparatus according to claim 5, wherein said first D/A converter generates analog data by dividing a whole voltage by a number based on the predetermined number of bits to produce discrete voltage values and by assigning each of the voltage values to each digital data represented by said predetermined number of bits.