Patent ID: 8724382

Claim:
A personal digital assistant (PDA) comprising: a plurality of non-volatile multiple-bit per cell (MBC) memory apparatuses operably connected by a bus, each memory apparatus including: a memory array including an electrically erasable block having a reprogrammable page; the reprogrammable page comprising upper and lower pages sharing common word-lines; the upper and lower pages including respective upper and lower data fields; the upper and lower data fields including respective virtual upper and lower cells of MBC memory cells; the MBC memory cells having respective threshold voltages programmable to a selected one of first level, second level, third level, and fourth level in order from the lowest voltage level, the lower cell having the respective threshold voltage from the first threshold voltage level to the second threshold voltage level, and the upper cells having the respective threshold voltage from the first threshold voltage level to the fourth threshold voltage level or from the second threshold voltage level to the third threshold voltage level; and a controller configured to write data to the memory array, the controller being configured to control polarity by selectively inverting data to maximize a number of the bits within the lower page to be programmed and selectively inverting data to minimize a number of bits to be programmed in the upper page.