Method and apparatus for generating a seed set in a data dependent seed selector

• US 7,158,058 B1
• Filed: 07/20/2004
• Issued: 01/02/2007
• Est. Priority Date: 12/09/2002
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Yu, Zhan
• Primary Examiner(s): NGUYEN, LINH V
• Application Number:
  US10/894,864
• Time in Patent Office: 896 Days
• Field of Search: 341 50-107, 714/777, 714/761, 714/746, 714/758, 714/739, 714/738, 714/742, 714/268
• US Class Current: 341/58
• CPC Class Codes: G11B 20/10 Digital recording or reproducing
• CPC Class Codes: G11B 20/10009 Improvement or modification of read or write signals
• CPC Class Codes: G11B 20/1426 conversion to or from block codes or representations thereof
• CPC Class Codes: G11B 20/1866 by interleaving G11B20/1809 takes precedence
• CPC Class Codes: H03M 5/145 Conversion to or from block codes or representations thereof

Abstract

A communications channel includes a buffer that receives user data symbols including a plurality of M-bit symbols. A seed selector receives the plurality of M-bit symbols, selectively removes symbols from a seed set based on Hamming distances between at least two of the M-bit symbols, and selects a scrambling seed from remaining symbols in the seed set. A scrambling device that communicates with the seed selector and the data buffer generates scrambled user data based on the user data symbols and the scrambling seed. The communications channel is implemented in a data storage system. The seed selector ensures a minimum Hamming weight of 15 percent in the scrambled user data. The seed selector compares first and second user data symbols in the plurality of M-bit symbols.

Claims

1. A communications channel that includes a buffer that receives user data symbols including a plurality of M-bit symbols, comprising:

a seed selector that receives said plurality of M-bit symbols, that selectively removes symbols from a seed set based on Hamming distances between at least two of said M-bit symbols, and that selects a scrambling seed from remaining symbols in said seed set;

a scrambling device that communicates with said seed selector and said data buffer and that generates scrambled user data based on said user data symbols and said scrambling seed.

2. The communications channel of claim 1 wherein said communications channel is implemented in a data storage system.

3. The communications channel of claim 1 wherein said seed selector ensures a minimum Hamming weight of 15 percent in said scrambled user data.

4. The communications channel of claim 1 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols.

5. The communications channel of claim 4 wherein said seed selector removes said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

6. The communications channel of claim 4 wherein said seed selector removes said first and second user data symbols from said seed set, and symbols from said seed set that have Hamming distances of one from said first and second user data symbols when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

7. The communications channel of claim 4 wherein said seed selector removes said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

8. The communications channel of claim 4 wherein said seed selector removes said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

9. The communications channel of claim 4 wherein said seed selector removes said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, a fourth user data symbol from said seed set that is adjacent to said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

10. The communications channel of claim 4 wherein said seed selector removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

11. The communications channel of claim 4 wherein said seed selector removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol and said second user data symbol when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

12. The communications channel of claim 4 wherein said seed selector removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

13. The communications channel of claim 4 wherein said seed selector removes said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is adjacent to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

14. The communications channel of claim 4 wherein said seed selector removes said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is sequential to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, a fourth user data symbol from said seed set that is sequential to said third user data symbol, a third symbol from said seed set that is the one'"'"'s complement of said fourth user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

15. The communications channel of claim 1 further comprising:

an error correction coding (ECC) encoder (ENC) that communicates with said scrambling device and said seed selector, wherein said ECC ENC appends at least one of cyclic redundancy check (CRC) code, ECC, and said scrambling seed to said scrambled user data.

16. The communications channel of claim 1 wherein said scrambling device generates said scrambled user data by determining a bit-wise exclusive-OR (XOR) of said scrambling seed and said user data symbols.

17. A communications channel that includes a buffer that receives user data symbols including a plurality of M-bit symbols, comprising:

seed selecting means for receiving said plurality of M-bit symbols, for selectively removing symbols from a seed set based on Hamming distances between at least two of said M-bit symbols, and for selecting a scrambling seed from remaining symbols in said seed set;

scrambling means that communicates with said seed selecting means and the data buffer for generating scrambled user data based on said user data symbols and said scrambling seed.

18. The communications channel of claim 17 wherein said communications channel is implemented in a data storage system.

19. The communications channel of claim 17 wherein said seed selecting means ensures a minimum Hamming weight of 15 percent in said scrambled user data.

20. The communications channel of claim 17 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols.

21. The communications channel of claim 20 wherein said seed selecting means removes said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

22. The communications channel of claim 20 wherein said seed selecting means removes said first and second user data symbols from said seed set, and symbols from said seed set that have Hamming distances of one from said first and second user data symbols when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

23. The communications channel of claim 20 wherein said seed selecting means removes said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

24. The communications channel of claim 20 wherein said seed selecting means removes said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

25. The communications channel of claim 20 wherein said seed selecting means removes said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, a fourth user data symbol from said seed set that is adjacent to said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

26. The communications channel of claim 20 wherein said seed selecting means removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

27. The communications channel of claim 20 wherein said seed selecting means removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol and said second user data symbol when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

28. The communications channel of claim 20 wherein said seed selecting means removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

29. The communications channel of claim 20 wherein said seed selecting means removes said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is adjacent to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

30. The communications channel of claim 20 wherein said seed selecting means removes said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is sequential to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, a fourth user data symbol from said seed set that is sequential to said third user data symbol, a third symbol from said seed set that is the one'"'"'s complement of said fourth user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

31. The communications channel of claim 17 further comprising:

error correction coding (ECC) means that communicates with said scrambling means and said seed selecting means for appending at least one of cyclic redundancy check (CRC) code, ECC bits, and said scrambling seed to said scrambled user data.

32. The communications channel of claim 17 wherein said scrambling means generates said scrambled user data by determining a bit-wise exclusive-OR (XOR) of said scrambling seed and said user data symbols.

33. A method for operating a communications channel that includes a buffer that receives user data symbols including a plurality of M-bit symbols, comprising:

receiving said plurality of M-bit symbols;

selectively removing symbols from a seed set based on Hamming distances between at least two of said M-bit symbols;

selecting a scrambling seed from remaining symbols in said seed set;

generating scrambled user data based on said user data symbols and said scrambling seed.

34. The method of claim 33 wherein said communications channel is implemented in a data storage system.

35. The method of claim 33 wherein said scrambled user data has a minimum Hamming weight of 15 percent in said scrambled user data.

36. The method of claim 33 further comprising comparing first and second user data symbols in said plurality of M-bit symbols.

37. The method of claim 36 further comprising removing said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

38. The method of claim 36 further comprising removing said first and second user data symbols from said seed set, and symbols from said seed set that have Hamming distances of one from said first and second user data symbols when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

39. The method of claim 36 further comprising removing said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

40. The method of claim 36 further comprising removing said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

41. The method of claim 36 further comprising removing said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, a fourth user data symbol from said seed set that is adjacent to said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

42. The method of claim 36 further comprising removing said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

43. The method of claim 36 further comprising removing said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol and said second user data symbol when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

44. The method of claim 36 further comprising removing said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

45. The method of claim 36 further comprising removing said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is adjacent to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

46. The method of claim 36 further comprising removing said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is sequential to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, a fourth user data symbol from said seed set that is sequential to said third user data symbol, a third symbol from said seed set that is the one'"'"'s complement of said fourth user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

47. The method of claim 33 further comprising appending at least one of cyclic redundancy check (CRC) code, ECC bits, and said scrambling seed to said scrambled user data.

48. The method of claim 33 further comprising generating said scrambled user data by determining a bit-wise exclusive-OR (XOR) of said scrambling seed and said user data symbols.

49. A data scrambler, comprising:

a seed selector that receives user data including M-bit symbols, that includes a seed set containing symbols, and that selects a scrambling seed from symbols in said seed set based on Hamming distances between at least two of said M-bit symbols; and

a scrambling device that communicates with said seed selector and that generates scrambled user data based on said user data and said scrambling seed.

50. The data scrambler of claim 49 wherein said seed selector selectively removes symbols from said seed set based on Hamming distances between at least two of said M-bit symbols and selects said scrambling seed from remaining symbols in said seed set.

51. A data storage system comprising the data scrambler of claim 49.

52. The data scrambler of claim 49 wherein said seed selector ensures a minimum Hamming weight of 15 percent in said scrambled user data.

53. The data scrambler of claim 49 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selector removes said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

54. The data scrambler of claim 49 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selector removes said first and second user data symbols from said seed set, and symbols from said seed set that have Hamming distances of one from said first and second user data symbols when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

55. The data scrambler of claim 49 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selector removes said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

56. The data scrambler of claim 49 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selector removes said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

57. The data scrambler of claim 49 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selector removes said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, a fourth user data symbol from said seed set that is adjacent to said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

58. The data scrambler of claim 49 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selector removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

59. The data scrambler of claim 49 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selector removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol and said second user data symbol when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

60. The data scrambler of claim 49 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selector removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

61. The data scrambler of claim 49 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selector removes said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is adjacent to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

62. The data scrambler of claim 49 wherein said seed selector compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selector removes said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is sequential to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, a fourth user data symbol from said seed set that is sequential to said third user data symbol, a third symbol from said seed set that is the one'"'"'s complement of said fourth user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

63. A system comprising the data scrambler of claim 49 and further comprising:

an error correction coding (ECC) encoder (ENC) that communicates with said scrambling device and said seed selector, wherein said ECC ENC appends at least one of cyclic redundancy check (CRC) code, ECC, and said scrambling seed to said scrambled user data.

64. The data scrambler of claim 49 wherein said scrambling device generates said scrambled user data by determining a bit-wise exclusive-OR (XOR) of said scrambling seed and said user data symbols.

65. A system comprising:

a data scrambler that receives user data including M-bit symbols and that scrambles said user data using a scrambling seed that is selected from symbols in a seed set based on Hamming distances between at least two of said M-bit symbols; and

an error correction coding (ECC) encoder (ENC) that communicates with said scrambler and that appends at least one of cyclic redundancy check (CRC) code, ECC, and said scrambling seed to said scrambled user data.

66. The system of claim 65 wherein said data scrambler includes a seed selector that receives said user data including said M-bit symbols, that includes said seed set containing symbols, and that selects said scrambling seed from symbols in said seed set based on Hamming distances between at least two of said M-bit symbols.

67. The system of claim 66 wherein said data scrambler further includes a scrambling device that communicates with said seed selector and that generates said scrambled user data based on said user data and said scrambling seed.

68. The system of claim 67 wherein said seed selector selectively removes symbols from said seed set based on Hamming distances between at least two of said M-bit symbols and selects said scrambling seed from remaining symbols in said seed set.

69. The system of claim 65 wherein said data scrambler is implemented in a data storage system.

70. A data scrambler, comprising:

seed selecting means for receiving user data including M-bit symbols, and for selecting a scrambling seed from symbols in a seed set based on Hamming distances between at least two of said M-bit symbols; and

scrambling means that communicates with said seed selecting means for generating scrambled user data based on said user data and said scrambling seed.

71. The data scrambler of claim 70 wherein said seed selecting means selectively removes symbols from said seed set based on Hamming distances between at least two of said M-bit symbols and selects said scrambling seed from remaining symbols in said seed set.

72. A data storage system comprising the data scrambler of claim 70.

73. The data scrambler of claim 70 wherein said seed selecting means ensures a minimum Hamming weight of 15 percent in said scrambled user data.

74. The data scrambler of claim 70 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selecting means removes said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

75. The data scrambler of claim 70 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selecting means removes said first and second user data symbols from said seed set, and symbols from said seed set that have Hamming distances of one from said first and second user data symbols when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

76. The data scrambler of claim 70 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selecting means removes said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

77. The data scrambler of claim 70 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selecting means removes said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

78. The data scrambler of claim 70 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selecting means removes said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, a fourth user data symbol from said seed set that is adjacent to said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

79. The data scrambler of claim 70 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selecting means removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

80. The data scrambler of claim 70 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selecting means removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol and said second user data symbol when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

81. The data scrambler of claim 70 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selecting means removes said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

82. The data scrambler of claim 70 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selecting means removes said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is adjacent to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

83. The data scrambler of claim 70 wherein said seed selecting means compares first and second user data symbols in said plurality of M-bit symbols and wherein said seed selecting means removes said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is sequential to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, a fourth user data symbol from said seed set that is sequential to said third user data symbol, a third symbol from said seed set that is the one'"'"'s complement of said fourth user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

84. A system comprising the data scrambler of claim 70 and further comprising:

error correction coding (ECC) encoding means, that communicates with said scrambling means and said seed selecting means, for appending at least one of cyclic redundancy check (CRC) code, ECC, and said scrambling seed to said scrambled user data.

85. The data scrambler of claim 70 wherein said scrambling means generates said scrambled user data by determining a bit-wise exclusive-OR (XOR) of said scrambling seed and said user data symbols.

86. A system comprising:

data scrambling means for receiving user data including M-bit symbols and for scrambling said user data using a scrambling seed that is selected from symbols in a seed set based on Hamming distances between at least two of said M-bit symbols; and

error correction coding (ECC) encoding means (ENC), that communicates with said scrambling means, for appending at least one of cyclic redundancy check (CRC) code, ECC, and said scrambling seed to said scrambled user data.

87. The system of claim 86 wherein said data scrambling means includes seed selecting means for receiving said user data including said M-bit symbols, and for selecting said scrambling seed from symbols in a seed set based on Hamming distances between at least two of said M-bit symbols.

88. The system of claim 87 wherein said data scrambling means further includes scrambling means, that communicates with said seed selecting means, for generating said scrambled user data based on said user data and said scrambling seed.

89. The system of claim 88 wherein said seed selecting means selectively removes symbols from said seed set based on Hamming distances between at least two of said M-bit symbols and selects said scrambling seed from remaining symbols in said seed set.

90. The system of claim 86 wherein said data scrambling means is implemented in a data storage system.

91. A method for operating a data scrambler, comprising:

receiving user data including M-bit symbols;

selecting a scrambling seed from symbols in a seed set based on Hamming distances between at least two of said M-bit symbols; and

generating scrambled user data based on said user data and said scrambling seed.

92. The method of claim 91 further comprising:

selectively removing symbols from said seed set based on Hamming distances between at least two of said M-bit symbols; and

selecting said scrambling seed from remaining symbols in said seed set.

93. The method of claim 91 further comprising ensuring a minimum Hamming weight of 15 percent in said scrambled user data.

94. The method of claim 91 further comprising:

comparing first and second user data symbols in said plurality of M-bit symbols; and

removing said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

95. The method of claim 91 further comprising:

comparing first and second user data symbols in said plurality of M-bit symbols; and

removing said first and second user data symbols from said seed set, and symbols from said seed set that have Hamming distances of one from said first and second user data symbols when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

96. The method of claim 91 further comprising:

comparing first and second user data symbols in said plurality of M-bit symbols; and

removing said first and second user data symbols from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

97. The method of claim 91 further comprising:

comparing first and second user data symbols in said plurality of M-bit symbols; and

removing said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

98. The method of claim 91 further comprising:

comparing first and second user data symbols in said plurality of M-bit symbols; and

removing said first user data symbol from said seed set, a third user data symbol from said seed set that is adjacent to said second user data symbol, a fourth user data symbol from said seed set that is adjacent to said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

99. The method of claim 91 further comprising:

comparing first and second user data symbols in said plurality of M-bit symbols; and

removing said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is greater than or equal to three.

100. The method of claim 91 further comprising:

comparing first and second user data symbols in said plurality of M-bit symbols; and

removing said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol and said second user data symbol when a Hamming distance between said first user data symbol and said second user data symbol is equal to two.

101. The method of claim 91 further comprising:

comparing first and second user data symbols in said plurality of M-bit symbols; and

removing said first and second user data symbols from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, and a second symbol from said seed set that is the one'"'"'s complement of said second user data symbol from said seed set when a Hamming distance between said first user data symbol and said second user data symbol is equal to one.

102. The method of claim 91 further comprising:

comparing first and second user data symbols in said plurality of M-bit symbols; and

removing said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is adjacent to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

103. The method of claim 91 further comprising:

comparing first and second user data symbols in said plurality of M-bit symbols; and

removing said first user data symbol from said seed set, a first symbol from said seed set that is the one'"'"'s complement of said first user data symbol, a third user data symbol from said seed set that is sequential to said second user data symbol, a second symbol from said seed set that is the one'"'"'s complement of said third user data symbol, a fourth user data symbol from said seed set that is sequential to said third user data symbol, a third symbol from said seed set that is the one'"'"'s complement of said fourth user data symbol, and symbols from said seed set that have Hamming distances of one from said first user data symbol when said first user data symbol is equal to said second user data symbol.

104. The method of claim 91 further comprising appending at least one of cyclic redundancy check (CRC) code, error correction code (ECC), and said scrambling seed to said scrambled user data.

105. The method of claim 91 further comprising generating said scrambled user data by determining a bit-wise exclusive-OR (XOR) of said scrambling seed and said user data symbols.

106. A method of operating a communications channel, comprising:

receiving user data including M-bit symbols;

scrambling said user data using a scrambling seed that is selected from symbols in a seed set based on Hamming distances between at least two of said M-bit symbols; and

appending at least one of cyclic redundancy check (CRC) code, error correction code (ECC), and said scrambling seed to said scrambled user data.