Method and apparatus for randomizing data in a direct access storage device

• US 4,993,029 A
• Filed: 03/13/1989
• Issued: 02/12/1991
• Est. Priority Date: 03/13/1989
• Status: Expired due to Term

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Heise, Nyles N., Galbraith, Richard L.
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): BEAUSOLIEL JR, ROBERT W
• Application Number:
  US07/322,588
• Time in Patent Office: 701 Days
• Field of Search: 371/40.1, 371/40.2, 371/38.1, 371/39.1, 371/2.1, 371/2.2, 360/38.1, 360/53, 360/48, 360/32, 358/336
• US Class Current: 714/769
• CPC Class Codes: G11B 20/10 Digital recording or reproducing
• CPC Class Codes: G11B 20/10009 Improvement or modification of read or write signals

Abstract

Data byte fields and corresponding ECC byte fields to be magnetically recorded as multi-byte records is randomized prior to run-length encoding. The randomized/encoded data is then written. When the randomized/encoded data is read back, the data is first decoded, and then derandomized in a complementary fashion. The randomizing avoids the writing of byte patterns that tend to stress the ability of a head/disk interface to record the data transitions at proper linear track positions. When reading, the complementary derandomizing scheme avoids presenting a repeating pattern of read-errors to the ECC network. Thus, read-errors are not propagated through the read channel. Data is randomized, and subsequently derandomized, in a repeating or pseudo random, complementary sequence for each byte. The complementary randomizing/derandomizing sequence is determined by the count contained in a counter. This counter is initialized at the beginning of a record, and is progressively incremented to the predetermined next count as each byte is processed. Data randomizing the first four bits of each byte are multiplied by the first four bits of an 8-bit counter, and the last four bits are multiplied by the last four counter bits. During derandomizing, division by way of multiplication-of-the-inverse is used, as the first four bits of each byte are multiplied by the inverse order of the last counter four bits, and the last four bits are multiplied by the inverse order of the first counter bits.

Claims

1. Binary data storage apparatus, comprising;

writing/reading transducer means associated with non volatile data storage media means to form a transducer/media interface,

a write channel having

first data-input means adapted for the reception of binary data to be written to said media means, said binary data comprising a plurality of multi-byte data fields,

second data-input means adapted for the reception of an identifying data field for each of said multi-byte data fields,

randomizer means having first input means connected to said first data-input means to thereby receive said multi-byte data fields, said randomizer means having second input means connected to said second data-input means and being responsive to said identifying data field to begin a repetitive sequence of data randomizing for each byte of said multi-byte data field, and providing an output comprising a plurality of randomized multi-byte data fields, and

means connecting said transducer/media interface to the output of said randomizer means and to said second data-input means, whereby randomized data comprising a plurality of multi-byte data fields, each data field including an identifying data field, is written on said non volatile media means, and

a read channel having

read interface means comprising said transducer/media interface whereby said randomized data is read back from said non volatile meadia means,

read-data input means connected to said transducer/media interface for the reception of said read-back randomized data,

identifying data detector means having an output, and having an input connected to said read-data input means for detecting the identifying data field of each read-data field, and

complementary derandomizer means having first input means connected to said read-data input means, to receive said randomized data, said derandomizer means having second input means connected to the output of said identifying data detector means, said derandomizer means being responsive to detection of an identifying data field to begin a complementary sequence of derandomizing of each byte of said read-data field.

2. The data storage apparatus of claim 1 wherein said data storage media means is magnetic disk storage means.

3. The data storage apparatus of claim 2 wherein said randomizer means and said derandomizer means include pseudo random counter means.

4. The data storage apparatus of claim 1, wherein the first data-input means of said write channel includes ECC network means, and wherein said read channel includes complementary ECC network means connected to the output of said derandomizer means.

5. The data storage apparatus of claim 4 wherein said randomizer means and said derandomizer means include complementary pseudo random counter means.

6. The data storage apparatus of claim 5 wherein said data storage media means is magnetic disk storage means.

7. The data storage apparatus of claim 1,

wherein the write channel means connecting said transducer/media interface to the output of said randomizer means includes encoder means, and

wherein the read channel read-data input means connecting said transducer/media interface for the reception of said multi-byte randomized data fields includes decoder means.

8. The data storage apparatus of claim 7 wherein said data storage media means is magnetic disk storage means.

9. The data storage apparatus of claim 8 wherein said randomizer means includes pseudo random counter means operable to multiply each byte of said multi-byte data field by a pseudo random polynomial function, and wherein said derandomizer means includes complementary pseudo random counter means operable to multiply said multi-byte read-data field in accordance with the inverse of said pseudo random polynomial function.

10. The data storage apparatus of claim 1,

wherein the first data-input means of said write channel includes ECC network means,

wherein said read channel includes complementary ECC network means connected to the output of said derandomizer means,

wherein the write channel means connecting said transducer/media interface to the output of said randomizer means includes encoder means, and

wherein the read channel read-data input means connected said transducer/media interface for the reception of said randomized data and said identification field includes decoder means.

11. The data storage apparatus of claim 10 wherein said randomizer means and said derandomizer means include pseudo random counter means.

12. The data storage apparatus of claim 11 wherein said data storage media means is magnetic disk storage means.

13. The data storage apparatus of claim 12 wherein said randomizer means includes a pseudo random counter means operable to multiply each byte of said multi-byte data field by a pseudo random polynomial function, and wherein said derandomizer means includes pseudo random counter means operable to multiply said multi-byte read-data field in accordance with the inverse of said pseudo random polynomial function.

14. A method for writing, and later reading, binary data and corresponding ECC data in a DASD magnetic recording device,

the writing steps of the method providing for data randomization in a manner to minimize the writing of data patterns that stress magnetic recording media within said DASD device, and

the reading steps of the method subsequently providing data derandomization in a manner to minimize read-error patterns that stress the ECC function,

the method comprising the steps of;

providing writing/reading transducer means associated with said magnetic recording media to form a transducer/media interface,

providing a write channel having

write-data input means adapted for the reception of binary data fields to be written to said magnetic recording media,

ECC network means having input means connected to said write-data input means, said ECC network means having output means,

randomizer means having input means connected to the output means of said ECC network means, said randomizer means having output means, and

means connecting said transducer/media interface to the output means of said randomizer means whereby randomized data fields may be stored on said magnetic recording media, and

providing a read channel having

read interface means comprising said transducer/media interface whereby said stored, randomized, data fields may be read back from said magnetic recording media,

read-data input means connected to said transducer/media interface for the reception of said randomized data fields,

complementary derandomizer means having input means connected to said read-data input means to receive said randomized data fields, said derandomizer means having output means,

complementary ECC network means connected to the output means of said derandomizer means, said complementary ECC network means having output means, and

read-data output means connected to the output means of said complementary ECC network means.

15. The method of claim 14 including the step of providing said magnetic recording media in the form of magnetic disk means.

16. The method of claim 14 including the step of providing said randomizer means and said derandomizer means in the form of pseudo random counter means.

17. The method of claim 16 including the step of providing said magnetic recording media in the form of magnetic disk means.

18. The data storage apparatus of claim 14 including the steps of

providing means for encoding the output of said randomizer means prior to writing said randomized data fields on said magnetic recording media, and

providing complementary decoder means connected to said read-data input means for the reception of said read-back randomized data fields.

19. The method of claim 18 including the step of providing said magnetic recording media in the form of magnetic disk means.

20. The method of claim 14 including the steps of

providing said randomizer means in the form of pseudo random counter means that is operable to multiply said binary data fields by a pseudo random polynomial function, and

providing said derandomizer means in the form of complementary pseudo random counter means that is operable to multiply said read-back randomized binary data fields in accordance with the inverse of said pseudo random polynomial function.

21. The data storage apparatus of claim 20 including the steps of

providing means for encoding the output of said randomizer means prior to writing said randomized data fields on said magnetic recording media, and

providing complementary decoder means connected to said read-data input means for the reception of said read-back randomized data fields.

22. The method claim 21 including the step of providing said magnetic recording means in the form of magnetic disk storage means.

23. A method of recording and subsequently reading a binary data record on magnetic recording media, comprising the steps of;

randomizing said data record,

run-length encoding said randomized data record, writing said randomized and encoded data record on said magnetic media,

reading said randomized and encoded data record back of off said magnetic media,

run-length decoding said read-back data record in a complementary fashion, and

derandomizing said decoded read-back data record in a complementary fashion.

24. The method of claim 23, wherein said data record comprises a multi-byte record, and including the steps of

randomizing said data record, and subsequently derandomizing said read-back data record, in a pseudo random complementary sequence for each byte of said data record and said read-back data record.

25. The method of claim 24 wherein the complementary randomizing/derandomizing sequence is determined by the binary count contained in a counter, the count of said counter being initialized at the beginning of said data record and said read-back data record, and said counter being progressively incremented to a next predetermined count as each byte of said multi-byte data record and each byte of said multi-byte read-back data record is progressively processed.

26. The method of claim 25 wherein said counter is an 8-bit counter, and including the steps of

during data randomizing multiplying the first four bits of each data record byte by the first four bits of said 8-bit counter, and multiplying the last four bits of each data record byte by the last four bits of said 8-bit counter, and

subsequently, during derandomizing of said read-back data record data, performing a multiplication-of-the-inverse process by multiplying the first four bits of each read-back data record byte by the inverse order of the last four bits of said 8-bit counter, and multiplying the last four bits of each read-back record byte by the inverse order of the first four bits of said 8-bit counter.