Todd C Hill

US Patent:

49791915, Dec 18, 1990

Filed:

May 17, 1989

Appl. No.:

7/352976

Inventors:

David G. Bond - Kent WA
Todd Hill - Tukwila WA
Paul D. Weis - Seattle WA
John R. Woods - Auburn WA

Assignee:

The Boeing Company - Seattle WA

International Classification:

H04L 700

US Classification:

375108

Abstract:

A fault tolerant clock system in which synchronization of the clocks continuing to operate after a fault occurs is maintained within a skew limit. The clock system includes a plurality of clock channels (10), each including a clock unit (12) and an isolation port (14). A local clock signal produced by a crystal oscillator (16) is enabled to provide a clock channel output signal while a counter (24) in the clock unit accumulates a predetermined number of local clock pulses. After the predetermined number is reached, the counter disables the clock channel output signal and produces a sync pulse, which is input to a voter block (48). In response to the second sync pulse to be received from each of the clock channels, each voter block produces a load pulse signal that is input to the isolation port of that clock channel. Corresponding isolated load signals are produced by the isolation port and provided to voter blocks (72) in each of the clock units. The voter blocks respond to the second isolated load signal to be received, producing a load enable signal that is input to the counter.

US Patent:

53496540, Sep 20, 1994

Filed:

Feb 20, 1992

Appl. No.:

7/839208

Inventors:

David G. Bond - Kent WA
Vincent A. Caluori - Kent WA
Todd Hill - Seattle WA
David T. Kirkland - Kent WA
Michael L. Raftery - Federal Way WA
Derek J. VanAlen - Kent WA

Assignee:

The Boeing Company - Seattle WA

International Classification:

G06F 1108

US Classification:

395575

Abstract:

A data exchange system for use in a system that includes a plurality of redundant channels (12). A data exchange unit (30) is provided to process data, ensuring that consistent data are used by each of the channels. The data exchange unit votes the data so that an output is provided that is identical in non-faulty channels. The data exchange units communicate over an inter-channel net that includes a consistency port (160), which serves as a separate second fault containment region for each channel, enabling the data exchange system to be Byzantine resilient. If input data are provided by a single one of the redundant channels, the data are distributed to each of the data exchange units for all channels in the system using two rounds of communication. However, if nominally identical data are input to each of the data exchange units in the redundant channels, a single round of communication and a simple voting process are used to determine a consistent output for each channel. A multiplexer (112) is used to select the data source for distribution to the consistency ports of each of the data exchange units.