Eeprom emulation in flash device
AssigneeSpansion LLC
InventorAllan Parker
Life of this patent
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Abstract
Flash memory systems and methodologies are provided herein for providing byte alterability in a flash device. Logical cell mapping is changed from using a single physical memory cell to using two adjacent physical cells as a logical cell for emulating byte alterability. By mapping two adjacent physical cells as a single logical cell, the logical cell is a combination of neighboring drain/source regions, thereby creating a single program and erase entity. The single program and erase entities can allow for logical cell erase and program in either direction of a low voltage state or a high voltage state on a single bit or variable bit length basis. By employing the single program and erase entity, the subject innovation can provide a cost-effective approach to emulating electrically EEPROM in a flash device.
Claims20
A method of emulating byte alterability in a flash device (100), comprising;
- changing a voltage state in a single program and erase entity (402) to a first voltage state on a basis of a single program and erase entity, the single program and erase entity comprising two adjacent dual bit physical memory cells (404, 406) of the flash device as a single logical cell;
- and
- changing the voltage state in the single program and erase entity to a second voltage state that is different from the first voltage state.
A method of emulating byte alterability in a flash device (100) comprising a plurality of dual bit memory cells, comprising;
- mapping two adjacent physical memory cells (404, 406) as a single program and erase entity (402);
- and
- programming a portion of or an entire of the flash memory on a basis of the single program and erase entity.
A flash device (3400) that emulates an electrically eraseable programmable read only memory, comprising:
- a plurality of single program and erase entities (3402) comprising two adjacent dual bit physical memory cells in the flash memory;
- one or more bitline decoders (3406) and wordline decoders (3408) that select one or more single program and erase entities for operating the flash memory device on a basis of the single program and erase entity, the bitline decoders comprising a table driven decoder.
Dependencies are inferred from the claim text.