US 4,380,761 AGranted

Digital phase decoder with collision detection

AssigneeXerox Corporation

InventorDavid R. Boggs

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Abstract

A data communication system includes a communicating medium and a plurality of transceivers connected to the medium, each including a transmitter for transmitting phase-encoded data onto the medium and a receiver for receiving phase-encoded data communicated on the medium by another transceiver. A digital phase decoder is coupled to the receiver of each transceiver for decoding the data received and applying at its output a decode signal representative of the character of the received data. The received data comprises a plurality of bitcells each of a predetermined time period with a predetermined number of bitcells representing a data packet. The decoder includes a combination signal generating means and counter means to ascertain, relative to each bitcell in a packet, where any transitional change has occurred in relation to each packet bitcell, the point of occurrence being representative of one of several possible conditions relative to the decoded signal, those conditions being indicative of either a data transition from a low state to a high state or a data transition from a high state to a low state or an illegal transition treated as a data collision.

Claims8

Dependent claims

A digital phase decoder for receiving and decoding phase encoded data transmitted as a plurality of bitcells, each of a predetermined time period, with a predetermined number of said bitcells representing a packet comprising

means for synchronizing received phase encoded data with the frequency of a predetermined clock signal having a rate exceeding the frequency of said bitcells,
means coupled to the output of said synchronizing means for developing a pair of output signals respectively indicative of a transitional change of a binary state of said received data,
means coupled to said developing means for generating a decode signal representative of one of several conditions due to a transitional change, said conditions being indicative of either a data transition from a low state to a high state or a data transition from a high state to a low state or an illegal transition treated as a data collision,
means for counting the number of clock intervals of said predetermined clock signal under the control of said generating means,
said generating means monitoring said counter means to ascertain relative to each bitcell period where a transitional change has occurred in relation therewith, the point of occurrence indicative of one of said several conditions.

2 more elements

Dependencies are inferred from the claim text.