The subject technology provides for scanning blocks of a flash memory device for erased pages. A first codeword read from a page of a block in a flash memory device is received and provided to a first decoder for decoding. In response to receiving a first success indicator from the first decoder indicating that the first codeword was successfully decoded, first decoded data is provided from the first decoder to a second decoder for verification of the first decoded data. In response to receiving a first failure indicator from the second decoder indicating that the first decoded data was not verified, the page of the block is identified as being in an erased state based on the first success indicator received from the first decoder and the first failure indicator received from the second decoder.

Apparatuses and methods for performing an error correction code (ECC) operation are provided. One example method can include encoding data by including parity data for a number of cross-over bits, wherein the number of cross-over bits are bits located at intersections of column codewords and row codewords.

An error correction circuit includes a control unit suitable for receiving a data chunk including a plurality of data blocks, each of the data blocks being included in a corresponding codeword of a first direction and a corresponding codeword of a second direction; and a decoder suitable for performing a decoding operation on a codeword, which is selected by the control unit, in the data chunk, wherein the control unit calculates a first reference value by applying a correction capability value of the first direction to a flag of the first direction, calculates a second reference value by applying a correction capability value of the second direction to a flag of the second direction, selects a priority direction from the first direction and the second direction based on the first reference value and the second reference value, and preferentially selects codewords of the priority direction for decoding operations.

A method and an apparatus are provided for decoding a polar code. A simplified successive cancellation list (SSCL) decoding tree for the polar code is generated. The SSCL decoding tree includes a plurality of nodes. One or more nodes of the plurality of nodes are identified as employing Reed-Muller codes for decoding. Decoding of received log-likelihood ratios (LLRs) is performed using Reed-Muller codes at the one or more nodes. Hard decision values are output from the one or more nodes.

An iterative decoding circuit is provided. The iterative decoding circuit includes a first concatenated decoding circuit, a second concatenated decoding circuit, and a comparator. The first concatenated decoding circuit includes a first convolutional decoder, a first deinterleaver, and a first block decoder. The second concatenated decoding circuit is coupled to the first concatenated decoding circuit, and the second concatenated decoding circuit includes a second convolutional decoder, a second deinterleaver, and a second block decoder. The comparator receives a first convolutional decoding result corresponding to a first convolutional decoding operation and a second convolutional decoding result of a second convolutional decoding operation, and is configured to compare the first convolutional decoding result with the second convolutional decoding result to generate a comparing result. The second block decoder obtains an erasure address information according to the comparing result.

Apparatuses and methods for performing an error correction code (ECC) operation are provided. One example method can include performing a first error code correction (ECC) operation on a portion of data, performing a second ECC operation on the portion of data in response to the first ECC operation failing, and performing a third ECC operation on the portion of data in response to the second ECC operation failing.

An iterative decoding circuit is provided. The iterative decoding circuit includes a first concatenated decoding circuit, a second concatenated decoding circuit, and a comparator. The first concatenated decoding circuit includes a first convolutional decoder, a first deinterleaver, and a first block decoder. The second concatenated decoding circuit is coupled to the first concatenated decoding circuit, and the second concatenated decoding circuit includes a second convolutional decoder, a second deinterleaver, and a second block decoder. The comparator receives a first convolutional decoding result corresponding to a first convolutional decoding operation and a second convolutional decoding result of a second convolutional decoding operation, and is configured to compare the first convolutional decoding result with the second convolutional decoding result to generate a comparing result. The second block decoder obtains an erasure address information according to the comparing result.

A set of bits of a data block that is associated with an unsuccessful first decoding operation may be identified. A second decoding operation to simulate switching at least one bit of the set of bits may be performed. At least one bit of the set of bits switched during the performance of the second decoding operation may be determined to correspond to an error. The error from the at least one bit of the set of bits may be corrected by changing a value of the at least one bit.

A memory system according to an embodiment includes a nonvolatile memory and a memory controller. The memory controller converts a received value read from the nonvolatile memory into first likelihood information by using a first conversion table, executes decoding on the first likelihood information and outputting a posterior value, outputs an estimated value of the received value obtained on the basis of the posterior value in a case where the decoding is successful. The memory controller generates a second conversion table on the basis of the posterior value in a case where the decoding fails. The memory controller converts the received value into second likelihood information by using the second conversion table in a case where the second conversion table has been generated, and executes decoding on the second likelihood information and outputs a posterior value.

An encoder encodes input data utilizing a binary symmetry-invariant product code including D data bits and P parity bits in each dimension. The encoder includes a half-size data array including K subarrays each having multiple rows of storage for H bits of data, where D is an integer equal to 2H+1 and K is an integer that is 2 or greater. The encoder is configured to access K rows of data by reading a respective H-bit data word of input data from each of the multiple subarrays and K H-bit data words of duplicate data from across multiple different rows of the subarrays. The encoder further includes at least one register configured to receive the bits read from the half-size data array code and rotate them as needed, at least one row parity generator, and a column parity generator that generates column parities based on row parity.