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Synchronization for Zero Modulation Code

IP.com Disclosure Number: IPCOM000081774D
Original Publication Date: 1974-Aug-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Patel, AM: AUTHOR

Abstract

U. S. Patent 3,810,111 describes a Zero Modulation (ZM) code, in which each data bit is represented by two windows that contain a 1 to designate a waveform transition and a 0 to indicate the absence of a transition. The code has run-length constraints so that there are no adjacent 1 bits and not more than three adjacent 0 bits. It also has a charge constraint that the waveform is closely symmetrical about the zero axis, so that it can be transmitted through capacitive and inductive devices.

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Synchronization for Zero Modulation Code

U. S. Patent 3,810,111 describes a Zero Modulation (ZM) code, in which each data bit is represented by two windows that contain a 1 to designate a waveform transition and a 0 to indicate the absence of a transition. The code has run-length constraints so that there are no adjacent 1 bits and not more than three adjacent 0 bits. It also has a charge constraint that the waveform is closely symmetrical about the zero axis, so that it can be transmitted through capacitive and inductive devices.

Because there are two windows for each data bit, the detection circuits must establish clocking to identify occurrence of a window in the waveform, and must also identify whether a window is the first or the second of the two windows that represent a data bit. A special waveform can be used to synchronize the clock for operation on a subsequent waveform that represents data.

The synchronizing waveform may be distinguished from an ordinary data waveform by selecting a pattern that violates the charge constraint, but maintains the minimum and maximum run length constraints. The sequence is made short enough that charge accumulation is not a problem. The following two sequences are the minimum length sequences that violate the charge constraint. w = 00101000101000 w* = 00010100010100. That is, the occurrence of either of these waveforms violates the charge constraint, without regard to the charge value at the beginning of the sequence. Thu...