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Communication system enabling programmable logic controllers access to host computer tasks and host computer access to programmable logic controllers without polling

  • US 5,131,092 A
  • Filed: 09/01/1989
  • Issued: 07/14/1992
  • Est. Priority Date: 09/01/1989
  • Status: Expired due to Term
First Claim
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1. A high speed industrial control system comprising:

  • (a) a high speed data communications network;

    (b) a plurality of programmable logic controllers each of said programmable logic controllers executing a ladder program and includinga data bus,a scan processor coupled to said data bus for executing said ladder program,a control processor coupled to said data bus,an equivalent network interface module having a communications processor, said communications processor for sending messages from said programmable controller to said communications network and receiving messages from said communications network, a random access mailbox and a first port, said first port coupled to said high speed communications network, and a multi-port RAM having a first port coupled to said equivalent network interface module and a second port coupled to said data bus;

    (c) a host computer communicatively coupled to said high speed communications network, said host computer includingmeans for executing a plurality of programs responsive to said messages from said programmable logic controller,a plurality of tasks, one of said tasks associated with a respective one of said programs, each of said tasks including a respective mailbox for receiving unsolicited ones of said messages from said programmable logic controller for said particular task,a dispatcher communicatively coupled between said high speed data communications network and said tasks, anda global mailbox coupled to said dispatcher, said global mailbox for receiving unsolicited ones of said messages from said programmable logic controller directed to said global mailbox for use by any of said tasks;

    (d) wherein said programmable logic controller can communicate with said host computer'"'"'s plurality of tasks as though said tasks were other programmable logic controllers coupled to said communication network; and

    (e) wherein said host computer can receive said messages from said programmable logic controller without polling said programmable logic controller.

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