Encoding and decoding systems for binary data

Details Encoding and decoding systems for binary data Encoding and decoding systems for binary data

1982-02-11

1985-01-29

Miller, Charles D.

Communications: electrical

Audible indication

Percussion-type sound producer

360 40, H03K 1324

Patent

active

044969341

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to a binary data encoding system for converting a sequence of binary data to a sequence of binary codes suitable for the recording original binary data on a record medium such as a magnetic tape or a magnetic disc, and a decoding system for decoding and converting the sequence of converted binary codes upon reproducing it from the record medium.
In order to increase a recording density upon recording binary data on a record medium such as a magnetic tape or a magnetic disc there are previously proposed and practiced various encoding systems.
FIGS. 1(a)-(e) are explanatory diagrams of one example of a conventional encoding system. FIG. 1(a) shows one example of a bit pattern of an original binary data sequence wherein numerals 0 and 1 express logic "0" and "1" respectively and T.sub.o indicates a bit interval. FIGS. (b) and (d) are one example of conventional encoding systems; FIG. (b) is called an MFM system (modified FM system) and FIG. (d) is called a 3 PM system (3 position modulation system. As examples of sorts of appliances applied to the respective systems, the MFM system is used with magnetic disc devices (3330, 3340, 3350 etc.) of IBM and the 3 PM system is used with a magnetic disc device (8434) of Uniback. A conversion algorithm of the MFM system is to convert bits "1" and "0" of an original binary data sequence to "01" and "X0" respectively where "X" becomes a complementary logic (1.fwdarw.0 or 0.fwdarw.1) of a code bit just preceding thereto. Also, a conversion algorithm of the 3 PM system is to divide original data into 3-bit units to convert them to a 6-bit code as shown in the following 1st Table:


1ST TABLE ______________________________________ Conversion Algorithm of 3 PM System Original Converted Data Code Conditions ______________________________________ 000 000010 When a pattern of "101" 001 000100 is generated in a code 010 010000 sequence after the 011 010010 conversion it is 100 001000 changed to "010" 101 100000 110 100010 111 100100 ______________________________________
Furthermore a sequence of codes converted according to each of the encoding systems is such that recording currents are generated and recorded on a record medium so as to cause an inversion of magnetization with bits of "1" but not to cause an inversion of magnetization with bits of "0". FIGS. 1(c) and (e) are waveforms of the recording currents (NRZI signals) for the code sequences encoded according to the MFM system of FIG. (b) and the 3 PM systems of FIG. (d) respectively.
In the case where the recording is effected on a record medium,
(a) if a spacing between the inversions of magnetization (a recording wavelength) is shortened, then the magnetic transitions due to the leading and trailing inversions of magnetization interfere with each other so as to result in a cause for generating errors upon the decoding of a reproduced signal;
(b) even if a demodulation phase margin (Tw) (which will be described later) during the reproduction is small with respect to the spacing between the inversions of magnetization, the abovementioned errors are apt to be caused;
(c) if the spacing between the inversions of magnetization is long as compared with a period of a demodulating clock signal produced from a reproduced signal, then the demodulating clock signal can not be accurately produced from the reproduced signal and the abovementioned errors are apt to be caused; and
(d) if the spacing between the inversions of magnetization increases with respect to the ratio of its maximum to its minimum, then the reproduced signal increases in waveform interference (which is called a pattern peak shift) and the abovementioned errors are apt to be caused.
In general encoding systems, therefore, the undermentioned variables are given as the parameters indicating the ability system capability including the four items (a), (b), (c) and (d) as described above. Now assuming that in same encoding system, a sequence of m-bit binary data is converte

REFERENCES:
patent: 3852687 (1974-12-01), Hodges
patent: 4323931 (1982-04-01), Jacoby
patent: 4337458 (1982-06-01), Cohn
Miessler, "IBM Technical Disclosure Bulletin", vol. 17, No. 5, Oct. 1974, pp. 1489-1491.
Horiguchi, "IEEE Transactions on Magnetics", vol. MAG-12, No. 6, Nov. 1976, pp. 740-742.
Franaszek, "IBM Journal of Research and Development", Jul. 1970, pp. 376-383.

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