| 摘要 |
A data encoding system encodes data using the following d=7, k=2 code: -DATA BITS CODE WORDS -00 000X -01 0100 -10 100X -011 10000X -111 100100 -0000 1000000X - where X is a ONE if the last two bits of the preceding code word are both ZEROS and a ZERO otherwise, and the right-most bits are the first in time. The system encodes the data by encoding the first four bits of data to an eight-bit code word if the bits are all ZEROS and the last two bits of the previous code word are in a predetermined pattern. If the first four bits are not ZEROS and the system encodes the first three data bits to form a six-bit code word if the first two bits are both ONES. Otherwise, the system encodes the first two data bits to form a four-bit code word. The system selects the code word which preserves the code limited run length. The system also includes a data demodulator which demodulates data which is encoded according to the chart. The demodulator first sets the first two bits of encoded data to ZEROS. It then compares the first eight, six or four encoded bits to the code words and decodes the bits according to the code word chart. The code also allows the system to synchronize to the code words by finding appropriate bit patterns in the encoded data.
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