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Ternary Gray Code

IP.com Disclosure Number: IPCOM000075144D
Original Publication Date: 1971-Aug-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Maley, GA: AUTHOR [+2]

Abstract

A Gray code is a binary code that changes in only one bit position as it is advanced in count. Gray codes have two well-known application areas; analog-digital converters of the mechanical type and for the assignment of feedback loops in sequential circuits. In both of these applications, it is essential to use a Gray code to overcome ambiguities that otherwise appear as the code is advanced. These ambiguities result from the inability to design mechanical or electrical devices to simultaneously change signals on two or more lines. In the mechanical analog-digital converter area, the use of ternary rather than binary will reduce the number of required wires by 502. But, the problem with full-ternary Gray codes is that they do not close on themselves (See Fig. 1).

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Ternary Gray Code

A Gray code is a binary code that changes in only one bit position as it is advanced in count. Gray codes have two well-known application areas; analog- digital converters of the mechanical type and for the assignment of feedback loops in sequential circuits. In both of these applications, it is essential to use a Gray code to overcome ambiguities that otherwise appear as the code is advanced. These ambiguities result from the inability to design mechanical or electrical devices to simultaneously change signals on two or more lines. In the mechanical analog-digital converter area, the use of ternary rather than binary will reduce the number of required wires by 502. But, the problem with full- ternary Gray codes is that they do not close on themselves (See Fig. 1).

The solution to this closure problem is to use only an even number of the available states (See Fig. 2).

A further advantage of this method is that it lends itself to binary conversion. Two of these ternary positions contain eight states rather than the usual nine associated with ternary. A two-position ternary code wheel of this new type is shown in Fig. 3. It is assumed that the code wheel is read by two photocells. Each cell radds the white, gray or black area of each track and thus, two wires are sufficient to carry the eight positions of the code wheel.

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