Memory system and method for operating the same
A memory system and a method for operating the memory system, in which the memory system includes a semiconductor memory device for storing data, and for reading and outputting the stored data in a read operation, and a controller controlling the semiconductor memory device in the read operation, and sequentially performing first and second decoding operations on the data output from the semiconductor memory device, wherein the controller updates and stores a bin label codeword in the second decoding operation, and backs up and stores a start bin label codeword in the bin label codeword.
1. A memory system comprising:
a semiconductor memory device configured to store data, and read and output the stored data in a read operation; and
a controller configured to control the semiconductor memory device in the read operation, and sequentially perform first and second decoding operations on the data output from the semiconductor memory device,
wherein the controller updates and stores a bin label codeword in the second decoding operation, and backs up and stores a start bin label codeword in the bin label codeword.
2. The memory system of claim 1 , wherein the first decoding operation is a soft decision decoding operation.
3. The memory system of claim 1 , wherein the semiconductor memory device performs a read operation using a soft decision read voltage in the first decoding operation.
4. The memory system of claim 1 , wherein the second decoding operation includes a first additional soft decoding operation and a second additional soft decoding operation.
5. The memory system of claim 4 , wherein the semiconductor memory device:
performs at least one read operation using a new read voltage changed in a first direction from a start read voltage in the first additional soft decoding operation; and
performs at least one read operation using a new read voltage changed in a second direction from the start read voltage in the second additional soft decoding operation.
6. The memory system of claim 5 , wherein the controller includes:
an ECC unit configured to perform the first and second decoding operations; and
an ECC buffer configured to update and store the bin label codeword corresponding to the start read voltage and the new read voltage changed in the first direction in the first additional soft decoding operation, and back up and store the start bin label codeword corresponding to the start read voltage.
7. The memory system of claim 6 , wherein the ECC buffer includes:
a bin label buffer configured to update and store the bin label codeword; and
a backup buffer configured to back up the start bin label codeword in the read operation using the start read voltage during the first additional soft decoding operation.
8. The memory system of claim 7 , wherein the backup buffer moves the start bin label codeword stored in the second additional soft decoding operation to the bin label buffer.
9. The memory system of claim 8 , wherein the controller controls the semiconductor memory device to perform at least one read operation using the new read voltage changed in the second direction from the start read voltage, based on the start bin label codeword stored in the bin label buffer in the second additional soft decoding operation.
10. The memory system of claim 1 , wherein the bin label codeword is obtained by dividing threshold voltages of memory cells, which are acquired in a read operation during the second decoding operation, based on read voltages.
11. The memory system of claim 1 , wherein the controller performs a hard decision decoding operation before performing the first decoding operation.
12. A memory system comprising:
a semiconductor memory device configured to store data, and read and output the stored data in a read operation; and
a controller configured to perform a decoding operation on the data output from the semiconductor memory device,
wherein the controller includes:
an ECC unit configured to perform a soft decision decoding operation, and an additional soft decision decoding operation; and
an ECC buffer configured to update and store a bin label codeword in the additional soft decision decoding operation, and back up and store a start bin label codeword in the bin label codeword.
13. The memory system of claim 12 , wherein the semiconductor memory device performs a first read operation using a soft decision read voltage in the soft decision decoding operation.
14. The memory system of claim 12 , wherein the semiconductor memory device:
performs at least one second read operation using a new read voltage changed in a first direction from a start read voltage in a first additional soft decoding operation during the additional soft decision decoding operation; and
performs at least one third read operation using a new read voltage changed in a second direction from the start read voltage in a second additional soft decoding operation performed after the first additional soft decoding operation.
15. The memory system of claim 14 , wherein the ECC buffer includes:
a bin label buffer configured to update and store the bin label codeword; and
a backup buffer configured to back up the start bin label codeword in the read operation using the start read voltage during the first additional soft decoding operation.
16. The memory system of claim 15 , wherein the backup buffer moves the start bin label codeword stored in the second additional soft decoding operation to the bin label buffer.
17. The memory system of claim 16 , wherein the controller controls the semiconductor memory device to perform at least one read operation using the new read voltage decreased in the second direction from the start read voltage, based on the start bin label codeword stored in the bin label buffer in the second additional soft decoding operation.
18. The memory system of claim 12 , wherein the ECC unit performs a hard decision decoding operation before performing the soft decision decoding operation.
19. A method for operating a memory system, the method comprising:
performing a soft decision decoding operation;
when it is determined that the soft decision decoding operation has failed, performing a first additional soft decision decoding operation, updating and storing a plurality of bin label codewords including a start bin label codeword, and backing up and storing the start bin label codeword; and
when it is determined that the first additional soft decision decoding operation has failed, performing a second additional soft decision decoding operation, using the backed-up start bin label codeword.
20. The method of claim 19 , further comprising performing a hard decision decoding operation before performing the soft decision decoding operation.
21. The method of claim 20 , wherein, in the first additional soft decision decoding operation, soft decision data are read by performing at least one read operation using a new read voltage changed in a first direction from a start read voltage, and a soft decision decoding operation is performed based on the read soft decision data and hard decision data decoded in the hard decision decoding operation.
22. The method of claim 20 , wherein, in the second additional soft decision decoding operation, soft decision data are read by performing at least one read operation using a new read voltage changed in a second direction from the start read voltage, and a soft decision decoding operation is performed based on the read soft decision data and hard decision data decoded in the hard decision decoding operation.
23. The method of claim 22 , wherein, in the second additional soft decision decoding operation, the start read voltage is set using the backed-up start bin label codeword.