Multiplex communications – Wide area network – Packet switching
Patent
1993-06-24
1995-11-07
Chin, Wellington
Multiplex communications
Wide area network
Packet switching
370 17, 370 8514, 370108, 371 206, 371 205, H04L 1242, H04L 1264
Patent
active
054652502
ABSTRACT:
Embodiments of the present invention provide methods and circuits for testing the hybrid capabilities of a station before the station is connected into an FDDI-II hybrid ring. One embodiment tests hybrid mode operation of an FDDI-II non-monitor station by creating a loopback ring, generating cycles for isochronous transmission on the loopback ring, and measuring the progress of the cycles around the loopback ring. The loopback ring created may be internal to a single integrated circuit, internal to a single slave station, or limited to a pair of stations, such as a concentrator and a single attachment station. Another embodiment provides a circuit for use in station on an FDDI-II ring. The circuit includes a loopback circuit which may be configured to create a hybrid ring and a cycle generator for generating cycles on the hybrid ring. The cycle generator includes a small latency adjustment buffer (LAB) and a limited isochronous media access control unit (IMAC) which are incapable of cycle master operation but are sufficient to provide test cycles.
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National Semiconductor's Fiber Distributed Data Interface Designer's Guide, No. 103751, 1990 Edition, Santa Clara, Calif.
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FDDI Physical Layer Protocol (PHY-2), Draft Proposed American National Standard (ANSI), Rev. 5, Jun. 17, 1992.
FDDI Hybrid Ring Control (HRC), Draft Proposed American National Standard (ANSI), Rev. 6.2, May 28, 1992.
Chin Wellington
Millers David T.
National Semiconductor Corporation
Winters Paul J.
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