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Rate 4/5 Coding

IP.com Disclosure Number: IPCOM000060845D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Martin, GNN: AUTHOR

Abstract

Using the following convention for data bits and code bits: (Image Omitted) where the final bit of a code word has the same value as the final bit of the counterpart data word and is referred to by the same symbol "d", and, for clarity, "s" is used to denote the value of d in the previous code word and "j", the value of e in the next code word, encoding is performed by the following logic: (Image Omitted) This logic gives the following code word set, if "t" is the inverse of s: (Image Omitted) for use on a dicode channel, or for use interleaved on a PR4 channel assuming, additionally, the use of the NRZ convention, where a 1 in the channel strings signifies one direction of write current for one clock interval, and a 0, the opposite current.

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Rate 4/5 Coding

Using the following convention for data bits and code bits:

(Image Omitted)

where the final bit of a code word has the same value as the final bit of the counterpart data word and is referred to by the same symbol "d", and, for clarity, "s" is used to denote the value of d in the previous code word and "j", the value of e in the next code word, encoding is performed by the following logic:

(Image Omitted)

This logic gives the following code word set, if "t" is the inverse of s:

(Image Omitted)

for use on a dicode channel, or for use interleaved on a PR4 channel assuming, additionally, the use of the NRZ convention, where a 1 in the channel strings signifies one direction of write current for one clock interval, and a 0, the opposite current. Good timing and tracking are provided by the code being constrained to no more than three consecutive like symbols. Four data bits encode to a 5-bit channel word. A single error event can corrupt at most two channel words. To limit error propagation, each channel word can be decoded in isolation. A single error event will either corrupt a single code bit, or it will change the string in such a way that it is possible to determine which code words have been affected. One of the four data bits appears unchanged in the code word which enables the use of this bit as the parity bit in aconvolution code designed to operate on the code string. One possible form of the decoding logic is as follows:

(Image Omitted)

If...