Method and apparatus for long-term multi-valued storage in dynamic analog memory

In an analog multi-valued memory comprising analog storage means, an apparatus for refreshing the analog value on said analog storage means defining the state of said analog multi-valued memory comprising:

• means for obtaining a binary quantization value corresponding to said analog value, said binary quantization value being in either a first or a second state;
• and
• means for increasing said analog value by a first fixed amount, if said binary quantization value is in said first state, and for decreasing said analog value by a second fixed amount, if said binary quantization value is in said second state.

A method for maintaining an analog value near one of a plurality of discrete levels, said method comprising repeating the step of:

• either increasing or decreasing said analog value by pre-selected amounts, with said analog value being increased or decreased depending on said analog value.

A method for refreshing an analog value stored in an analog value storage means, said method comprising the steps of:

• generating a binary value in response to an analog value stored in the analog storage means, said binary value being in either a first state or a second state, with the state of said binary value being determined from said analog value in a consistent and substantially repeatable manner;
• and
• increasing said analog value by a first pre-selected amount, if said binary value is in said first state, and decreasing said analog value by a second pre-selected amount, if said binary value is in said second state.