Rockwell Automation 1769-SM2 Compact I/O DSI/Modbus Communication Module - Manual (Page 76)

5-12 Understanding Explicit Messaging
RSLogix 500 Modbus RTU Master Write Message Example
Figure 5.9 shows an example Modbus RTU Master write message setup
screen. See Table 5.D for descriptions of the message configuration data.
Figure 5.9 RSLogix 500 Example Modbus RTU Master Write Message Setup Screen
In this example, Logic Command and Reference are being written to a
PowerFlex 70 drive. N7:100 through N7:106 (note the send length is 14
bytes or 7 words) contain the command data where:
Note the Size in Bytes (Receive) is set to “0” because no data is returned
for a write message.
For additional information about Modbus RTU write messages for
PowerFlex 7-Class drives, refer to the 20-COMM-H Adapter User
Manual, publication 20COMM-UM009.
Data Word Example Value Description
N7:100 15 PowerFlex 70 node address
N7:101 16 Function Code – Write Multiple Registers
N7:102 0 Starting Register Address (40001)
N7:103 3 Number of registers to write
N7:104 18 Value for 40001 – Logic Command word
N7:105 0 Value for 40002 – not used
N7:106 8192 Value for 40003 – Reference word