No assignee for patent application serial number 426980 has been made.
News editors obtained the following quote from the background information supplied by the inventors: "Non-volatile data storage devices, such as universal serial bus (USB) flash memory devices or removable storage cards, have allowed for increased portability of data and software applications. Flash memory devices can enhance data storage density by storing multiple bits in each flash memory cell. For example,
"One of the reasons for bit errors in MLC devices is merging of threshold voltage distribution profiles of different programmable states of MLC cells. Merging of threshold voltage distribution profiles of different states can be due to effects such as cycling (e.g. a number of write/erase cycles) or effects such as 'data retention' (e.g. a loss of charge of a floating gate of a transistor of a flash memory cell over time that results in a reduction in the cell's threshold voltage). Some of these bit errors can be converted to erasures by performing a 'soft' read of MLC cells according to an offset voltage .DELTA.V.sub.t. To illustrate, a 'hard' read may determine a hard bit value of a cell based on whether the cell has a threshold voltage above or below a read voltage V.sub.1. A 'soft' read may be performed at a read voltage V.sub.1+.DELTA.V.sub.t and/or at a read voltage V.sub.1-.DELTA.V.sub.t to obtain one or more soft bit values.
"If a hard bit value read from a cell differs from a soft bit value read from the cell, a threshold voltage of the cell is near a boundary between cell states. The hard bit value read from the cell may therefore be considered less reliable (as compared to a hard bit value read from a cell having a threshold voltage in a center of a cell state), resulting in an 'erasure,' also referred to as a soft bit error. Erasures may result from cells that exhibit hard bit errors because the cells have drifted from an initial state to a neighboring state (Error/Erasure). However, erasures may also result from cells that have approached, but have not crossed, a state boundary and that do not exhibit hard bit errors (Erasure/No-Error)."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "Erasure correction of data including a possibly corrupted ECC codeword may be performed prior to ECC decoding by using single error detection (SED) parity bits and soft read information. If a portion of the data includes a single erasure bit and also fails a parity check using a SED parity bit, a bit value of the erasure bit is changed. A resulting updated ECC codeword may be provided to an ECC decoder with a reduced number of bit errors. Error correction capability resulting from using a number of SED parity bits may exceed an error correction capability provided by the same number of ECC parity bits.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1 is a block diagram of a particular illustrative embodiment of a system including a data storage device configured to correct erasures using single error detection parity;
"FIG. 2 is a diagram illustrating a particular embodiment of single error detection parity encoding that may be used by the data storage device of FIG. 1;
"FIG. 3 is a diagram illustrating a particular embodiment of erasure correction using the single error detection parity encoding of FIG. 2;
"FIG. 4 is a diagram illustrating erasures in data arising from a soft read operation and erasure correction using a single error detection process;
"FIG. 5 is a flow chart of a particular illustrative embodiment of a method of error correction using single error detection parity; and
"FIG. 6 is a flow chart of a particular illustrative embodiment of a method of encoding data for error correction using single error detection parity."
For additional information on this patent application, see: DESIREDDI, SATEESH. Erasure Correction Using Single Error Detection Parity. U.S. Patent Application Serial Number 426980, filed
Keywords for this news article include: Patents, Information Technology, Information and
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