Systems and methods for correlation based data alignment

1. A data processing system, the system comprising:

a sample buffer circuit operable to store a sample data set;

a data detector circuit operable to apply a data detection algorithm to the sample data set to yield a detected output, wherein a fragment of the sample data set is mis-aligned;

a data decoder circuit operable to apply a data decoding algorithm to a decoder input to yield an interim output, wherein the decoder input is derived from the detected output; and

a mis-alignment determination circuit operable to determine a mis-alignment value of the sample data set based upon a combination of the detected output and the interim output, wherein the mis-alignment determination circuit includes:

a threshold comparison circuit operable to compare instances of the interim output with a threshold value to yield a signature, wherein the signature includes a set of reliable correlation bits and corresponding reliable bit positions; and

a correlation circuit operable to identify a position in the detected output that exhibits a correlation to the signature.

2. The data processing system of claim 1 , the system further comprising:

a sync mark detection circuit operable to identify a sync mark in a received data set; and

wherein a mis-alignment of the sample data set is caused by a failure of the sync mark detection circuit to identify the sync mark in the received data set.

3. The data processing system of claim 1 , wherein the correlation circuit is further operable to calculate the mis-alignment value based upon the identified position in the detected output.

4. The data processing system of claim 1 , wherein the interim output includes soft data for bit positions generated as part of applying the data decoding algorithm.

5. The data processing system of claim 1 , wherein the sample data set is a fragment of a first codeword associated with a parity codeword, wherein the sample buffer is further operable to store a second codeword associated with the parity codeword, and the parity codeword, and wherein the interim output includes parity information generated based at least in part on the parity codeword and the second codeword.

6. The data processing system of claim 1 , wherein the sample data set is a fragment of a first codeword associated with a parity codeword, wherein the sample buffer is further operable to store a second codeword associated with the parity codeword, and the parity codeword, and wherein the interim output includes soft data for bit positions generated based at least in part on a combination of the parity codeword and the second codeword.

7. The data processing system of claim 1 , wherein the data decoder circuit is a low density parity check decoder circuit.

8. The data processing system of claim 1 , wherein the data detector circuit is a maximum a posteriori data detector circuit.

9. The data processing system of claim 1 , wherein the sample buffer circuit is operable to re-align the sample data set based at least in part on the mis-alignment value of the sample data set.

10. The data processing system of claim 1 , wherein the system is implemented as part of an integrated circuit.

11. The data processing system of claim 1 , wherein the system is incorporated in a hard disk drive including a storage medium and a read/write head assembly disposed in relation to the storage medium.

12. A method for data processing, the method comprising:

storing a sample data set to a storage buffer circuit, wherein the sample data set is mis-aligned;

applying a data detection circuit to the sample data set to yield a detected output;

applying a data decoding circuit to a decoder input to yield an interim output, wherein the decoder input is derived from the detected output;

using a correlation circuit to:

generate a correlation value corresponding to a difference between the detected output and a signature, wherein the signature is derived from the interim output;

determine a correlation occurrence based at least in part on the correlation value; and

determine a mis-alignment value for the correlation occurrence; and

using a sync mark detection circuit to identify a sync mark in a received data set, wherein a mis-alignment of the sample data set is caused by a failure of the sync mark detection circuit to identify the sync mark in the received data set; and

re-aligning the sample data set to yield a re-aligned sample data set, wherein the sample data set if re-aligned based at least in part on one or both of (i) the mis-alignment value and (ii) the failure to identify the sync mark in the received data set.

13. The method of claim 12 , wherein the method further comprises:

comparing instances of the interim output with a threshold value to yield the signature, wherein the signature includes a set of reliable correlation bits and corresponding reliable bit positions.

14. The method of claim 12 , wherein the detected output is a first detected output and the decoder input is a first decoder input, the method further comprising:

applying the data detection algorithm to the re-aligned sample data set to yield a second detected output; and

applying the data decoding algorithm to a second decoder input to yield a decoded output, wherein the second decoder input is derived from the second detected output.

15. The method of claim 12 , the method further comprising:

applying a sync mark detection to an input data set to identify a sync mark within the input data set, wherein the sample data set corresponds to the input data set; and

wherein the mis-alignment of the sample data set results from a failure to detect a sync mark within an expected range of elements of the input data set.

16. The method of claim 12 , wherein the correlation value is a Euclidean distance between the detected output and the signature, and wherein the correlation occurrence occurs at a position where the Euclidean distance is less than a threshold value.

17. The method of claim 16 , wherein the threshold value is user programmable.

18. A storage device, the storage device comprising:

a storage medium;

a read/write head disposed in relation to the storage medium and operable to provide an analog input corresponding to information sensed on the storage medium;

a read channel circuit, the read channel circuit including:

an analog processing circuit operable to generate a sample data set based upon the analog input;

a sample buffer circuit operable to store the sample data set, wherein a fragment of the sample data set is mis-aligned;

a data detector circuit operable to apply a data detection algorithm to the sample data set to yield a detected output, wherein a fragment of the sample data set is mis-aligned;

a data decoder circuit operable to apply a data decoding algorithm to a decoder input to yield an interim output, wherein the decoder input is derived from the detected output; and

a mis-alignment determination circuit operable to determine a mis-alignment value of the sample data set based upon a combination of the detected output and the interim output.

19. The storage device of claim 18 , wherein the mis-alignment determination circuit includes:

a threshold comparison circuit operable to compare instances of the interim output with a threshold value to yield a signature, wherein the signature includes a set of reliable correlation bits and corresponding reliable bit positions; and

a correlation circuit operable to:

identify a position in the detected output that exhibits a correlation to the signature; and

calculate the mis-alignment value based upon the identified position in the detected output.

20. The method of claim 13 , wherein the method further comprises:

identifying a position in the detected output that exhibits a correlation to the signature.