Multiplex communications – Wide area network – Packet switching
Patent
1981-04-16
1983-11-22
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370 94, 370 1, 370 16, 364200, 34082501, H04J 600
Patent
active
044173342
ABSTRACT:
A data processing system employing broadcast packet switching and having a plurality of subsystems and a system bus for linking the subsystems. The subsystems are grouped within stations that are each enclosed by a computer cabinet. The system bus includes a star coupler, first and second external transmission lines connecting each station to the star coupler, and first and second internal transmission lines within each station that are coupled to the first and second external transmission lines. The subsystems within each station are each coupled to the first and second internal transmission lines by a system bus interface. The system bus interface monitors the system bus for an idle condition, and passes a message from its subsystem to the system bus only when it detects an idle condition on the system bus. Each message on the system bus includes a postamble that is garbled by any system bus interface that detects an error in any message on the system bus. Each subsystem has a local memory that includes a mailbox for storing header information of messages that are to be copied by that subsystem. DMA circuitry in each system bus interface manages the operation of the mailbox in its subsystem. In alternate embodiments, the star coupler may be a magnetic star coupler or an electrical star coupler, and the system bus may be comprised of two channels, each channel including a star coupler and pairs of transmission lines connecting each station to the star coupler.
REFERENCES:
patent: 3803405 (1974-04-01), Ohnsorge et al.
patent: 3859465 (1975-01-01), Schenkel et al.
patent: 4119804 (1978-10-01), Hafner et al.
patent: 4254496 (1981-03-01), Munter
patent: 4276643 (1981-06-01), Laprie
patent: 4340775 (1982-07-01), Gesek et al.
D. Lewin: "Theory and Design of Digital Computer Systems", 2nd Edition, pp. 396-397 (1980).
Gunderson Robert O.
Kocol James E.
Schuck David B.
Cavender J. T.
Dugas Edward
Jewett Stephen F.
NCR Corporation
Olms Douglas W.
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