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Agile mode for Modbus network protocol

  • US 6,880,015 B1
  • Filed: 02/25/2000
  • Issued: 04/12/2005
  • Est. Priority Date: 02/25/2000
  • Status: Expired due to Term
First Claim
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1. A Modbus slave device operable in an agile mode, the slave device being capable of receiving, interpreting, and responding to first-type and second-type message frames, the slave device comprising:

  • means for detecting a master query message frame generated by a master device;

    means, responsive to a first incoming character of the master query message frame, for setting a message-type control bit to a first value if the first incoming character is a prompt character for the first-type message frame, and for setting the message-type control bit to a second value if the first incoming character is not the prompt character for the first-type message frame;

    means for interpreting the master query message frame as the first-type message frame if the message-type control bit has the first value and as the second-type message frame if the message-type control bit has the second value;

    means for performing a command associated with the master query message frame if the slave device is addressed in the master query message frame; and

    means for generating a slave message frame responding to the master query message frame if the slave device is addressed in the master query message frame and the command requires a response, the slave message frame being of the first-type message frame if the message-type control bit has the first value, the slave message frame being of the second-type message frame if the message-type control bit has the second value.

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