Storage device performing error correction and operating method of storage device
Disclosed is a storage device which includes a nonvolatile memory device, and a memory controller that performs a read operation on the nonvolatile memory device and performs an error correction operation on data read in the read operation. In the error correction operation, the memory controller estimates an error rate of the read data, and determines whether to perform a read retry operation based on the estimated error rate.
1. A storage device comprising:
a nonvolatile memory device; and
a memory controller configured to,
perform a read operation on the nonvolatile memory device, and
perform an error correction operation on data read in the read operation by,
estimating an error rate of the read data,
in response to the estimated error rate being greater than a threshold value, omitting a hard decision decoding operation and performing a read retry operation, and
in response to the estimated error rate being less than or equal to the threshold value, performing the hard decision decoding operation.
2. The storage device of claim 1 , wherein the memory controller is configured to:
calculate a syndrome vector by multiplying the read data and a parity check matrix together; and
estimate a ratio of “1” in the syndrome vector as the error rate.
3. The storage device of claim 1 , wherein the memory controller is configured to perform a first soft decision decoding operation following the read retry operation.
4. The storage device of claim 1 , wherein, the memory controller is configured to, in the hard decision decoding operation, perform a low density parity check (LDPC) decoding operation on the read data.
5. The storage device of claim 4 , wherein the memory controller is configured to:
perform the LDPC decoding operation through a plurality of loops; and
at a first time between the plurality of loops, estimate a second error rate from a result of the LDPC decoding operation of the first time.
6. The storage device of claim 5 , wherein, the memory controller is configured to, in response to the estimated second error rate being greater than a first threshold value:
end the LDPC decoding operation; and
determine that the LDPC decoding operation fails in error correction.
7. The storage device of claim 6 , wherein,
the memory controller is configured to, at a second time after the first time between the plurality of loops, estimate a third error rate from a result of the LDPC decoding operation of the second time, and
the memory controller is configured to, in response to the estimated third error rate is greater than a second threshold value, end the LDPC decoding operation, and determine that the LDPC decoding operation fails in error correction.
8. The storage device of claim 7 , wherein the second threshold value is smaller than the first threshold value.
9. The storage device of claim 4 , wherein, the memory controller is configured to, in the hard decision decoding operation and in response to a first LDPC decoding operation for the read data failing, perform valley search and a second LDPC decoding operation.
10. The storage device of claim 1 , wherein,
the memory controller is configured to, in the read retry operation, send a read command to the nonvolatile memory device,
the nonvolatile memory device is configured to, in response to the read command, perform a second read operation, and send first data and second data to the memory controller, and
the memory controller is configured to perform a low density parity check (LDPC) decoding operation based on the read data, the first data, and the second data.
11. The storage device of claim 10 , wherein
a size of the first data is equal to a size of the read data, and
a size of the second data is equal to the size of the read data.
12. The storage device of claim 10 , wherein
the first data correspond to data read by using a read level lower than a read level of the read operation, and
the second data correspond to data read by using a read level higher than the read level of the read operation.
13. The storage device of claim 1 , wherein, the memory controller is configured to, in response to the error correction operation failing in the hard decision decoding operation or in a first soft decision decoding operation following the read retry operation, perform a second read retry operation and a low density parity check (LDPC) decoding operation for the read data.
14. The storage device of claim 13 , wherein,
the memory controller is configured to, in the second read retry operation, send a first read command and a second read command to the nonvolatile memory device,
the nonvolatile memory device is configured to
perform a first read operation in response to the first read command,
send first data to the memory controller,
perform a second read operation in response to the second read command, and
send second data to the memory controller, and
the memory controller is configured to perform the LDPC decoding operation based on the read data, the first data, and the second data.
15. A storage device comprising:
a nonvolatile memory device; and
a memory controller configured to,
perform a read operation on the nonvolatile memory device, and
perform an error correction operation on data read in the read operation by,
estimating an error rate of the read data,
in response to the estimated error rate being greater than a threshold value, omitting a low density parity check (LDPC) decoding operation for the read data and performing a read retry operation of reading additional data from the nonvolatile memory device, and
in response to the estimated error rate being less than or equal to the threshold value, performing the LDPC decoding operation.
16. The storage device of claim 15 , wherein, the memory controller is configured to, after performing the read retry operation, perform a soft decision decoding operation based on the read data and the additional data.
17. The storage device of claim 15 , wherein,
the memory controller is configured to, in the read retry operation, send one read command to the nonvolatile memory device,
the nonvolatile memory device is configured to perform one read operation, and send the additional data including first data and second data as a result of the one read operation to the memory controller,
a size of the first data is equal to a size of the read data, and
a size of the second data is equal to the size of the read data.
18. An operating method of operating a storage device including a nonvolatile memory device and a memory controller, the method comprising:
sending, at the memory controller, a first read command to the nonvolatile memory device;
performing, at the nonvolatile memory device, a first read operation in response to the first read command and sending first data as a result of the first read operation to the memory controller;
estimating, at the memory controller, an error rate of the first data;
in response to the estimated error rate being equal to or smaller than a threshold value, performing, at the memory controller, a hard decision decoding operation on the first data; and
in response to the estimated error rate being greater than the threshold value, sending, at the memory controller, a second read command to the nonvolatile memory device.
19. The method of claim 18 , further comprising:
performing, at the nonvolatile memory device, a second read operation in response to the second read command and sending second data and third data as a result of the second read operation to the memory controller; and
performing, at the memory controller, a soft decision decoding operation based on the first data, the second data, and the third data.