Single merging bit DC-suppressed run length limited coding

A digital modulation method for modulating an original digital data to an NRZI bit sequence, the method comprising:

• (a) dividing the original digital data into data words, each data word having a length of m bits;
• (b) converting the data words to code words, each code word having a length of n bits, provided that n is greater than m, and that when a code word comprises two bits of value 1, an alignment of consecutive bits of value 0 inserted between the two bits of value 1 has a length in a range from 2 bits to k bits;
• (c) connecting the code words with a one-bit merging bit inserted between the code words, the merging bit having a bit value of 0;
• (d) selecting the merging bit as having a bit value of 1 when:
• (i) adjacent bits on both sides of the merging bit are 1s, and in this case, the adjacent bits are also changed to 0s;
• or
• (ii) when trailing P bits of a code word preceding the merging bit and leading Q bits of a code word following the merging bit are all 0s, provided that P+Q.gtoreq.k, and in this case, at least either one of the P bits and Q bits has a bit sequence of (00000), and the bit sequence (00000) is changed to (00100);
• and
• (e) converting the bit sequence of the connected code words to the NRZI bit sequence.

A digital modulation apparatus for modulating an original digital data to an NRZI bit sequence, said original digital data being divided into data words, each data word having a length of m bits, said apparatus comprising:

• means for converting said data words to code words, each code word having a length of n bits, provided that n is greater than m, and that when a code word comprises two bits of value 1, an alignment of consecutive bits of value 0 inserted between said two bits of value 1 has a length in a range from 2 bits to k bits;
• means for connecting said code words with a one-bit merging bit inserted between said code words, said merging bit normally being selected as having a bit value of 0;
• first means for selecting said merging bit as having a bit value of 1 when adjacent bits on both sides of said merging bit are 1s, and in this case, said adjacent bits are also changed to 0s;
• second means for selecting said merging bit as having a bit value of 1 when trailing P bits of a code word preceding said merging bit and leading Q bits of a code word following said merging bit are all 0s, provided that P=Q.gtoreq.k, and in this case, at least either one of said P bits and said Q bits has a bit sequence of (00000), and said bit sequence (00000) is changed to (00100);
• and
• means for converting said bit sequence of said connected code words to said NRZI bit sequence.

A digital demodulation method for demodulating an NRZI bit sequence to an original digital data, comprising:

• (a) demodulating said NRZI bit sequence to a code bit sequence containing a plurality of code words with a merging bit inserted between the code words;
• (b) detecting a merging bit;
• (c) changing adjacent bits on both sides of the merging bit to 1s when the merging bit is 1, and at the same time, three consecutive bits on both sides of the merging bit are 0s;
• (d) changing the third consecutive bits on both sides of the merging bit to 0s when the following conditions (i), (ii) and (iii) are met:
• (i) the merging bit is 1;
• (ii) a third bit on one side of the merging bit is 1;
• and
• (iii) an other side of the merging bit has a pattern other than a predetermined bit pattern,
• such that trailing P bits of a code word preceding the merging bit and leading Q bits of a code word following the merging bit are all 0s, provided that P+Q.gtoreq.k,
• (e) separating code words, each code word having a length of n bits;
• and
• (f) reconverting said code words to data words, each data word having a length of m bits, provided that n is greater than m, and that when a code word comprises two bits of value 1, an alignment of consecutive bits of value 0 inserted between said two bits of value 1 has a length in a range from 2 bits to k bits.

A digital demodulation apparatus for demodulating an NRZI bit sequence to an original digital data, comprising:

• means for demodulating said NRZI bit sequence to a code bit sequence containing a plurality of code words with a merging bit inserted between every two adjacent code words;
• means for detecting said merging bit;
• first means for changing adjacent bits on both sides of said merging bit to 1s when said merging bit is 1, and at the same time, three consecutive bits on both sides of said merging bit are 0s;
• second means for changing said three consecutive bits on both sides of said merging bit to 0s when the following conditions (i), (ii) and (iii) are met:
• (i) said merging bit is 1;
• (ii) a third bit on one side of said merging bit is 1;
• and
• (iii) an other side of said merging bit has a pattern other than a predetermined bit pattern,
• such that trailing P bits of a code word preceding said merging bit and leading Q bits of a code word following said merging bit are all 0s, provided that P+Q.gtoreq.k,
• means for separating code words, each code word having a length of n bits;
• and
• means for reconverting said code words to data words, each data word having a length of m bits, provided that n is greater than m, and that when a code word comprises two bits of value 1, an alignment of consecutive bits of value 0 inserted between said two bits of value 1 has a length in a range from 2 to k bits.