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System and method for accessing PLC data on demand

  • US 8,738,159 B2
  • Filed: 02/15/2005
  • Issued: 05/27/2014
  • Est. Priority Date: 03/15/2004
  • Status: Expired due to Fees
First Claim
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1. A method for providing programmable logic controller data on demand, the method comprising:

  • providing a programmable logic controller (PLC) having an internal memory and an external interface, wherein the external interface is implemented as a dynamic linked library (DLL) that provides direct memory access (DMA) transfers to and from the internal memory of the PLC;

    providing an external end user application executing on a processor external to the PLC, the application including an executable access code and a function call and operative to send the access code and the function call to the external interface of the PLC;

    receiving the access code and function call at the external interface of the PLC;

    responding to the access code by granting to the end user application by the PLC, access to the internal memory of the PLC,wherein, once the access code is received, the processor external to the PLC is operable to directly read from or write to, via asynchronous DMA transfers, the internal memory of the PLC with involvement of the PLC limited to executing the DLL.

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