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Method and apparatus for synchronizing data in a host memory with data in target MCU memory

  • US 5,680,542 A
  • Filed: 06/07/1995
  • Issued: 10/21/1997
  • Est. Priority Date: 06/07/1995
  • Status: Expired due to Fees
First Claim
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1. A method for synchronizing data in a Target Memory with a copy of that data located in a Host Memory on a Host Computer, wherein:

  • data is organized in the Target Memory in a plurality of Target Data Lines,each one of the plurality of Target Data Lines comprises a corresponding fixed number of bits,each one of the plurality of Target Data Lines is uniquely identified by a corresponding Target means for identification,each of the plurality of Target Data Lines has a corresponding Target Line Dirty Flag,data is organized in the Host Memory in a plurality of Host Data Lines,each one of the plurality of Host Data Lines comprises a corresponding fixed number of bits,each one of the plurality of Host Data Lines is uniquely identified by a corresponding host means for identification,each of the plurality of Host Data Lines has a corresponding Host Line Dirty Flag,each of the plurality of Host Data Lines corresponds to a different one of the plurality of Target Data Lines,said method comprising the steps of;

    a) determining whenever one or more bits in one of the plurality of Target Data Lines has been modified, wherein;

    the Target Data Line determined to have been modified is a Modified Target Data Line;

    b) whenever the Station Controller determines in step (a) that one or more bits of the Target Data Line have been modified, determining whether the corresponding Target Line Dirty Flag is set;

    c) whenever the Station Controller determines in step (a) that one or more bits in the Modified Target Data Line have been modified and that the corresponding Target Line Dirty Flag is determined in step (b) not to be set, the following substeps are performed;

    1) sending a First Message from the Station Controller to the Host Computer comprising an indication that the Modified Target Data Line has been modified, and2) setting the Target Line Dirty Flag corresponding to the Modified Target Data Line;

    d) whenever a First Message sent in step (c) is received by the Host Computer, setting a Host Line Dirty Flag corresponding to the Modified Target Data Line;

    e) sending a Second Message from the Host Computer to the Station Controller indicating the identity of a Host Data Line that has its corresponding Host Line Dirty Flag set;

    f) sending a Third Message from the Station Controller to the Host Computer in response to the Second Message received in step (f), wherein said Third Message comprises;

    an ordered sequence of bits corresponding to the bits in the Host Data Line requested in the Second Message, andmeans for identifying the Host Data Line that corresponds to the ordered sequence of bits in the Third Message;

    g) clearing the Target Line Dirty Flag corresponding to the Target Data Line corresponding to the Host Data Line identified by the Third Message sent in step (f);

    h) when the Third Message is received by the Host Computer, updating the Host Data Line identified by the Third Message with the ordered sequence of bits in the Third Message; and

    i) when the Third Message is received by the Host Computer, clearing the Host Line Dirty Flag corresponding to the Host Data Line identified by the Third Message.

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