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# Phase Modulated NRZI Code

IP.com Disclosure Number: IPCOM000078960D
Original Publication Date: 1973-Apr-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 8K

IBM

## Related People

Paul: AUTHOR [+2]

## Abstract

A code using phase modulated (PM) nonreturn to zero (NRZI) stores 5 bits in 6 transitions. For this code, a 0 is represented by no transition, a 1 by a positive going transition and a 2 by a negative going transition. A combination of five ternary digits form a word and a clock ternary digit is contained in each word pattern.

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Phase Modulated NRZI Code

A code using phase modulated (PM) nonreturn to zero (NRZI) stores 5 bits in 6 transitions. For this code, a 0 is represented by no transition, a 1 by a positive going transition and a 2 by a negative going transition. A combination of five ternary digits form a word and a clock ternary digit is contained in each word pattern.

In this code, there are never more than 3 consecutive zeros where two words join, and the code may be designated as a D = O, K - 3 code in the standard notation for run-length limited codes.

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NOTE: C is a clock cell; its transition polarity or its absence of a transition, is determined by whatever selection is necessary to make the next code word physically realizable.

Variations on the recording code may be accomplished by a

(1) Base-6 code, (d,k) = (0,3);

(2) (d,k) = (0,3) storing 8 bits in 9 transition periods;

(3) (d,k) = (0,3) code with simple logic for encoding and decoding; and

(4) approximation to (d,k) = (0,2).

For the base-6 code, a set of six triplets are used as follows: A = [001, 010, 011, 101, 110, 111].

As there are six patterns in A, a code having words composed of N triplets will have 6/N/ distinct words, each of which can be recorded in 3N clock periods.

The base-6 code with N=2 has rate and (d,k) constraints identical to the PMNRZI code described above.

For a higher density code, a seventh nonzero triplet, 100, as well as the six triplets in A may be employed.

In a simplified logic...