2-out-of-3 Selecting facility in a 3-computer system

• US 4,616,312 A
• Filed: 02/28/1983
• Issued: 10/07/1986
• Est. Priority Date: 03/10/1982
• Status: Expired due to Term

• Current Assignee: Alcatel SA (Nokia Corporation)
• Original Assignee: International Standard Electric Corporation (ITT, Inc.)
• Inventors: Uebel, Helmut
• Primary Examiner(s): Thomas, James D.
• Assistant Examiner(s): Niessen, William G.
• Application Number:
  US06/470,756
• Time in Patent Office: 1,317 Days
• Field of Search: 364/200, 364/900, 371/11, 371/36, 371/63, 371/67, 371/68
• US Class Current: 714/11
• CPC Class Codes: G05B 9/03 with multiple-channel loop, i.e. redundant control systems
• CPC Class Codes: G06F 11/181 Eliminating the failing redundant component
• CPC Class Codes: G06F 11/184 where the redundant components implement processing functionality

Abstract

A fail-safe 2-out-of-3 selecting facility for a 3-computer system is disclosed which is especially suitable for use together with microprocessors having a large number of outputs. The computers (R1 . . . R3) of the 3-computer system handle the same information in parallel but asynchronously, exchange their results, and compare them. The output buses (A1, A3) of two computers (R1, R3) transfer the results in nonequivalent form, and are connected to two data output channels (AK1, AK2) via separate transfer switches (U1, U2). Depending on the result of the comparisons performed in the computers, the output ports of faulty computers are disconnected and the transfer switches are controlled in such a way that the output port of a faulty computer is disconnected from the associated data output channel, and that the output port (A2) of the third computer (R2) is connected to this channel instead. Depending on which computer is to be replaced, the third computer (R2) delivers its information in uninverted or inverted form. The operation of the transfer switches can be monitored by a serial nonequivalence check on the information transfered over the data output channels (AK1, AK2).

Claims

1. 2-out-of-3 selecting facility for a 3-computer system in which all computers process the same information in parallel, and in which a result is delivered for further processing only if at least two of the computers have arrived at this result, said facility comprising an output port (A1 . . . A3) in each of the computers and a comparison data input port (E1 . . . E3) in each of the computers which is connected to the output ports of the other two computers for the transfer of the results produced by these computers, and comprising comparison circuitry in each of the computers for comparing the result produced by it with the results produced by the neighboring computers and providing a corresponding comparison indication, to a majority voting circuit (MS), connected to receive said comparison indication depending on the comparison indications from all computers, and comprising two separate transfer switches (U1, U2) which are controlled by the majority voting circuit, said computers having outlet ports and said facility having two separate data output channels whereby said majority voting circuit controls said two separate transfer switches to connect the output ports to said two separate data channels wherein the output port (A1) of one of the computers (R1) is permanently connected to one of the transfer switches (U1), while the output port (A3) of another computer (R3) is permanently connected to the other transfer switch (U2), and that the output port of the third computer (R2) is connected to both transfer switches and, in response to a control instruction from the majority voting circuit (MS), can be connected to the first data output channel (AK1) by said one of the transfer switches (U1) or to the second data channel (AK2) by the other transfer switch (U2,) the output port of the computer previously permanently connected to the respective transfer switch being disconnected from the associated data output channel and wherein with ports (A1, A3) permanently connected to the transfer switches (U1, U2,) the results produced by the associated computers (R1, R3) appear in nonequivalent form, and that at the output port (A2) of the third computer (R2) the result produced by the latter appears in uninverted or inverted form depending on a control instruction (JNV) from the majority voting circuit (MS) and wherein the two data output channels (AK1, AK2) have parallel-serial converters (PS1, PS2) connected thereto whose outputs are connected to the inputs of a serial nonequivalence check circuit (AP), and that the output ports of the computers and the computers themselves can be disconnected in response to the output signal (APS) from the nonequivalence check circuit.

2. A 2-out-of-3 selecting facility as claimed in claim 1, characterized in that the majority voting circuit (MS) contains a read-only memory in which all possible combinations of comparison indications of the three computers and associated control instructions for the transfer switches (U1, U2) and for the disconnectable output ports (A1 . . . A3) of the computers are stored, and that, if a comparison indication is present, the majority voting circuit delivers the associated control instructions.