Troubleshooting serial com 3-6 – Yaskawa F7 Modbus User Manual
Page 37
Troubleshooting Serial COM 3-6
5:
Verify the contents of the response message.
5.1:
Connect an oscilloscope between the controller R+ and R- terminals for RS422 and RS485 4-Wire networks or
between terminals R+/S+ and R-/S- for RS485 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 he signal levels adhere to the RS422/RS485 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 adheres 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 correct is valid
5.3.5:
Verify that the CRC is correctly calculated.