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Programmable controller with backup capability

  • US 5,313,386 A
  • Filed: 06/11/1992
  • Issued: 05/17/1994
  • Est. Priority Date: 06/11/1992
  • Status: Expired due to Fees
First Claim
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1. In a programmable controller having a memory which stores a control program and data, and a processor for executing the control program to receive data from input/output circuits which connect to a machine being controlled and for sending data to the input/output circuits for operating devices on the machine;

  • wherein the improvement comprises;

    an input means for receiving a first signal indicating that another programmable controller, which is connected to the same input/output circuits, requests to operate in an active mode;

    a first terminal for receiving a second signal indicating that the programmable controller is to operate in the active mode when a plurality of programmable controllers are requesting to operate in the active mode at substantially the same time;

    mode indicator means for designating that the programmable controller is to operate in the active mode in response to said input means not receiving the first signal, and in response to said input means receiving the first signal and to said first terminal receiving the second signal, otherwise said mode indicator means designating that the programmable controller is to operate in a backup mode; and

    an output means for transmitting a third signal to the other programmable controller when said mode indicator means designates that the programmable controller is to operate in the active mode, the third signal not being transmitted when said mode indicator means designates that the programmable controller is to operate in the backup mode.

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