Data writing method for writing data into block of multi-level cell NAND flash memory by skipping a portion of upper page addresses and storage system and controller using the same

A controller, for writing data into a block of a MLC NAND flash memory, wherein the block comprises a plurality of page addresses, the page addresses are categorized into a plurality of upper page addresses and a plurality of lower page addresses, and the writing speed of the lower page addresses is faster than the writing speed of the upper page addresses, the controller comprising:

• a microprocessor unit;
• a flash memory interface, coupled to the microprocessor unit;
• a buffer memory, coupled to the microprocessor unit;
• and
• a memory management module, coupled to the microprocessor unit and having a plurality of machine instructions executed by the microprocessor unit to execute a plurality of data writing steps to the MLC NAND flash memory, wherein the data writing steps comprise:
• (1) receiving a writing command and data to be written by the writing command;
• (2) obtaining a first page address from the block;
• (3) determining whether the first page address belongs to the lower page addresses of the block, wherein step (5) is executed if the first page address belongs to the lower page addresses of the block, and step (4) is executed if the first page address does not belong to the lower page addresses of the block;
• (4) determining whether a second page address, which belongs to the lower page addresses of the block and has a coupling relationship with the first page address, stores valid data written by a previous writing command, wherein if the second page address does not store the valid data written by the previous writing command, step (5) is executed, and if the second page address stores the valid data written by the previous writing command, step (6) is executed;
• (5) writing the data into the first page address;
• and
• (6) skipping the first page address and writing the data into a third page address, which belongs to the lower page addresses of the block and does not have the coupling relationship with the first page address, wherein the skipped first page address does not store data before the block is erased.

A storage system, comprising:

• a MLC NAND flash memory, having a plurality of blocks, wherein each of the blocks comprises a plurality of page addresses, the page addresses are categorized into a plurality of upper page addresses and a plurality of lower page addresses, and the writing speed of the lower page addresses is faster than the writing speed of the upper page addresses;
• a transmission connection interface;
• and
• a controller, coupled to the MLC NAND flash memory and the transmission connection interface, the controller executing a plurality of machine instructions of a memory management module to execute a plurality of data writing steps, wherein the data writing steps comprise:
• (1) receiving a writing command and data to be written by the writing command;
• (2) obtaining a first page address from the block;
• (3) determining whether the first page address belongs to the lower page addresses of the block, wherein step (5) is executed if the first page address belongs to the lower page addresses of the block, and step (4) is executed if the first page address does not belong to the lower page addresses of the block;
• (4) determining whether a second page address, which belongs to the lower page addresses of the block and has a coupling relationship with the first page address, stores valid data written by a previous writing command, wherein if the second page address does not store the valid data written by the previous writing command, step (5) is executed, and if the second page address stores the valid data written by the previous writing command, step (6) is executed;
• (5) writing the data into the first page address;
• and
• (6) skipping the first page address and writing the data into a third page address, which belongs to the lower page addresses of the block and does not have the coupling relationship with the first page address, wherein the skipped first page address does not store data before the block is erased.