Yaskawa G7 Modbus Communication User Manual

Page 39

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.

[

] [

]

[

] [

]

[

] [

]

[

] [

]

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.