Method for programming a reference cell

In an integrated circuit memory having a plurality of memory cells each exhibiting a native threshold voltage value, a method for programming a reference cell comprising the steps of:

• a) locating an address for the memory cell having the highest native threshold voltage value (VTNH) by applying a first gate voltage value at which at least one memory cell fails a first preselected read operation and increasing the applied gate voltage until a final gate voltage value is reached at which each of the memory cells can just pass the first preselected read operation;
• b) programming the reference cell a predetermined amount;
• c) sensing the program state of the reference cell relative to the VTNH memory cell by performing a second preselected read operation on the reference cell;
• and
• d) repeating steps b) and c) until the sensing step indicates that the reference cell has been programmed an amount sufficient to fail the second preselected read operation.

A method for programming a set of reference cells for use in performing respective read operations on an integrated circuit memory having a plurality of memory cells, comprising the steps of:

• a) locating the cell in the memory array having the highest native threshold voltage value (VTNH);
• b) determining a voltage level for a reference voltage read signal relative to the VTNH cell;
• c) adjusting a reference voltage erase verify signal relative to the reference voltage read signal;
• and
• d) adjusting a reference voltage program verify signal relative to the reference voltage read signal.