FIELD OF THE INVENTION

The present invention relates to a technique for data storage, and more particularly to a data storage device and a plane selection method thereof.

BACKGROUND OF THE INVENTION

A data storage device, such as a solid state drive (SSD), a secure digital (SD) memory card or a portable flash memory, mainly is constituted by a control unit and a data storage medium. The data storage medium is constituted by a plurality of dies which are enabled by Chip Enable (CE) of the control unit. Each die has a plurality of planes, and the planes have a plurality of data columns for storing data.

Inevitably, secondary products may be produced in the manufacturing process of data storage devices. Therefore, it is necessary to screen all the bad columns in the data storage medium and record the bad columns in a bad column summary table before shipping the secondary products to market. According to the bad column summary table, the control unit is prevented from accessing these bad columns so as to avoid data access error during operation.

In general, the data storage device uses an error correcting code (ECC) to correct its stored data. However, a number of the bad columns which is provided by a hardware is limited duo to a size of memory. When the limited number of the bad columns is evenly distributed to each of plurality of planes, some planes having more bad columns may not be corrected by ECC.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide a plane selection method for a data storage device. The plane selection method can effectively use a limited number of the bad columns, and thereby optimizing a distribution of the bad columns onto planes.

The present invention provides a plane selection method which is applied to a data storage medium. The data storage medium includes a plurality of planes, each of the planes includes a plurality of blocks, each of the blocks includes a plurality of pages, and each of the pages which includes a plurality of data columns is divided into a plurality of chunks. The plane selection method includes steps of: defining at least one data column having a largest number of error bits in a worst chunk as a bad column until a quantity of bad columns is used up; determining whether at least two planes are uncorrectable according to a distribution of the bad columns; and eliminating a record of the bad columns and banning a worse plane which had the most bad columns than other planes.

The present invention further provides a plane selection method which is applied to a data storage medium. The data storage medium includes a plurality of planes, each of the planes includes a plurality of blocks, each of the blocks includes a plurality of pages, and each of the pages which includes a plurality of data columns is divided into a plurality of chunks. The plane selection method includes steps of: defining at least one data column having a largest number of error bits in a worst chunk as a bad column until a quantity of bad columns is used up; determining whether at least one plane is uncorrectable according to a distribution of the bad columns; and eliminating a record of the bad columns and banning a worst plane which had the most bad columns than other planes.

The present invention further provides a data storage device, which includes a controller and a data storage medium. The data storage medium includes a plurality of planes, each of the planes includes a plurality of blocks, each of the blocks includes a plurality of pages, and each of the pages which includes a plurality of data columns is divided into a plurality of chunks. A plane selection method is executed by the control unit including: defining at least one data column having a largest number of error bits in a worst chunk as a bad column until a quantity of bad columns is used up; determining whether at least two planes are uncorrectable according to a distribution of the bad columns; and eliminating a record of the bad columns and banning a worst plane which had the most bad columns than other planes.

The present invention further provides a data storage device with a plane summary table, which includes a controller and a data storage medium. The data storage medium includes a plurality of planes, each of the planes includes a plurality of blocks, each of the blocks includes a plurality of pages, and each of the pages which includes a plurality of data columns is divided into a plurality of chunks. A plane selection method is executed by the control unit including: defining at least one data column having a largest number of error bits in a worst chunk as a bad column until a quantity of bad columns is used up; determining whether at least one plane is uncorrectable according to a distribution of the bad columns; and eliminating a record of the bad columns and banning a worst plane which had the most bad columns than other planes.

In summary, the plane selection method for the data storage device provided by the present invention can leave a bad plane, ban other planes which are uncorrectable and use all the bad columns onto the bad plane, or ban all the planes which are uncorrectable and distribute the limited number of the bad columns onto other planes, so that the number of the bad columns can be effectively used and the distribution of the bad columns can be optimized.

