YASKAWA G7 Modbus Communication Manual page 39

5: Verify the contents of the response message.
5.1: Connect an oscilloscope between the controller R+ and R- terminals for RS-422 and RS-485 4-Wire networks or
between terminals R+/S+ and R-/S- for RS-485 2-wire networks.
5.1.1: Verify that the message pulse train exists and contains the correct number of pulses. Refer to the chapter
Message Formats for information on the message contents.
5.1.2: Verify that the signal levels adhere to the RS-422/RS-485 standard.
5.2: Capture the response message in hexadecimal format and record it below.
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5.3: Verify that the contents of the message adhere to the Modbus format as described previously.
5.3.1: Verify that the node address is valid.
5.3.2: Verify that the function code is valid.
5.3.3: Verify that the register address is valid.
5.3.4: Verify that the number of data bytes is valid.
5.3.5: Verify that the CRC is correctly calculated.
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