Coded data generation or conversion – Digital code to digital code converters – To or from run length limited codes
Patent
1990-05-21
1991-09-10
Deboer, Todd E.
Coded data generation or conversion
Digital code to digital code converters
To or from run length limited codes
360 39, H03M 700
Patent
active
050477676
ABSTRACT:
The present invention comprises the hardware implementation of an algorithm for a run length limited (1,7) block code of rate 2/3, wherein 2 unconstrained bits are mapped onto 3 constrained bits. The encoded data stream has a minimum of 1 "zero" between adjacent "ones", and a maximum of seven "zeros" between adjacent "ones". Unlike earlier (1,7) block encoders, the encoder of the present invention is a 4 state machine whose internal state description requires only 2 bits, rather than the 3 bits as taught in the prior art. The 4 state encoder combines the 2 incoming data bits with present state information to generate the output encoded sequence, and the next state designation. Error propagation due to a single channel bit error is limited to 5 bits.
The decoder of the invention utilizes three, 3 bit shift registers which hold 9 bits of the encoded data; each group of three bits is decoded into 2 bits corresponding to the original input bits by means of a logic array fed from the three shift registers.
REFERENCES:
patent: 4413251 (1983-11-01), Adler et al.
patent: 4488142 (1984-12-01), Franaszek
patent: 4684921 (1987-08-01), Fok et al.
patent: 4688016 (1987-08-01), Fok
Swanson Robert D.
Weathers Anthony D.
Deboer Todd E.
Eastman Kodak Company
Hoff Marc. S.
Monteith Dennis P.
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