Control of memory devices possessing variable resistance characteristics

A method of controlling a memory device comprising:

• applying a constant current source electrically in series with a memory cell during a programming operation;
• and
• applying a first voltage across the memory cell to set an impedance state of the memory cell, the impedance state representing information content, the first voltage determined by the constant current source.

A method of controlling a memory device comprising:

• applying a constant voltage source electrically in parallel with a memory cell during an erasing operation, the constant voltage source having a voltage level sufficient to erase the memory cell, the voltage level remains constant while an impedance state of the memory changes due to the erasing operation;
• and
• determining one or more desired impedance states that represents information content of the memory cell.