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Two-Wire, Balanced, Self-Clocking Binary Transmission Code

IP.com Disclosure Number: IPCOM000035641D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 57K

Publishing Venue

IBM

Related People

Balliet, L: AUTHOR

Abstract

This article describes a two-wire transmission system that limits frequency spectrum and radiated noise while still providing self-clocking, balanced error detection properties.

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Two-Wire, Balanced, Self-Clocking Binary Transmission Code

This article describes a two-wire transmission system that limits frequency spectrum and radiated noise while still providing self-clocking, balanced error detection properties.

Ideally, a serial digital transmission code will have the following properties: 1) low frequency spectrum 2) high signal-to-noise ratio 3) self-clocking characteristics (many transitions) 4) balanced number of logic one and zeros for AC coupling and optimum detection 5) error detection properties

Many bit coding techniques have some of these properties but not all. For example, non-return to zero (NRZ) has a low frequency spectrum and high signal-to-noise ratio but does not provide self-clocking, balance or error detection. Biphase codes have poor (high) frequency spectrum but exhibit all the other desirable features. In some applications, such as communication between electronic units on automotive vehicles, the spectrum should be kept low.

A two-wire system (such as a twisted pair system) is disclosed herein that provides all of the desired transmission characteristics cited above. The two wires are encoded in a binary two level format in accordance with the following:

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To maintain balance which provides for an equal number of zeros and ones on each line, the parameter "C" is defined as the accumulative sum of previous values for each line. The algorithm would be in accordance with the following rules: 1) Each binary "1" would alternate for line 1/line 2 between 1/0 and 0/1. 2) Each binary "0" would similarly alternate between 1/1 and 0/0. 3) The first bit can be arbitrary. 4) The first bit with a binary value different than the binary value of the first bit is determined to minimize "C". An example sequence is illustrated in Fig. 1. The system has the following characteristics: 1) There is a tra...