Rate 24/25 modulation code for PRML recording channels
AssigneeQuantum Corporation
InventorsKevin D. Fisher, James Fitzpatrick
Life of this patent
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Abstract
Rate 24/25 modulation encoding methods and apparatus improve efficiency in a PRML magnetic recording channel. The rate 24/25 code word uses rate 8/9 RLL encoding of one byte of user data, combined with interleaved unencoded bytes to achieve improved code rates with reasonable global run length constraint. Use of the the rate 8/9 RLL (0,3) subcode results in a rate 24/25 RLL (0,11) code, while a rate 8/9 (0,6/5) subcode results in a rate 24/25 RLL (0,14/13) code.
Claims21
A method for generating a rate 24/25 RLL (0,14/13) channel code for use in a digitally detected magnetic recording and playback system to encode a series of user digital data bits, the method comprising the steps of:
- forming a series of at least 24 bits of the user data bits;
- rate 8/9 encoding a first 8 bits of the series so as to form an encoded 9-bit codeword;
- partitioning the encoded 9-bit codeword so as to form a first, 5-bit nibble and a second, 4-bit nibble;
- sequentially concatenating the first nibble, a second 8-bits of the user data bits, the second nibble, and a third 8-bits of the user data bits so as to form a 25-bit codeword responsive to the 24 bits of user data.
A rate 24/25 modulation code for a magnetic recording channel comprising the bit sequence:
- A8:A4,B7:B0,A3:A0,C7:C0 where A8:A0 comprise a rate 8/9 codeword encoding a first 8-bit user byte and B and C are second and third 8-bit user bytes, respectively, of a three byte sequence of user data to be stored through the said magnetic recording channel.
A modulation code encoder for generating a rate 24/25 modulation code to encode digital data bits in a magnetic recording system comprising:
- a serial to parallel converter for receiving a serial stream of input data bits and forming a three-byte input word;
- a rate 8/9 encoder arranged for encoding a first byte of the input word to form a 9-bit codeword;
- and
- a register coupled to the serial-to-parallel converter to receive a second byte and a third byte of the input word, and coupled to the rate 8/9 encoder to receive the 9-bit codeword;
- the register being arranged to form the rate 24/25 codeword by concatenating the following bits in the following sequence:
- A8:4! B A3:0! C, where A is the 9-bit codeword, B is the second byte of the input word and C is the third byte of the input word.
A decoder for decoding a rate 24/25 modulation encoded serial stream of read data recovered from a magnetic recording medium, the decoder comprising:
- a serial to parallel converter for receiving the serial stream of read data and framing a 25-bit word;
- a rate 8/9 RLL decoder arranged for decoding a first 9 bits of the word to recover an 8-bit symbol;
- and
- a register coupled to the serial-to-parallel converter to receive a remaining 16 bits of the word, and coupled to the rate 8/9 encoder to receive the 8-bit symbol;
- the register being arranged to form a 24-bit decoded word by concatenating the following bits in the following sequence:
- A B C, where A is the said 8-bit symbol, B is the second byte of the input word and C is the third byte of the input word.
Dependencies are inferred from the claim text.