Rockwell Automation 1769-SM2 Compact I/O DSI/Modbus Communication Module - Manual (Page 78)

5-14 Understanding Explicit Messaging
RSLogix 5000 Modbus RTU Master Write Message Example
Figure 5.11 shows an example Modbus RTU Master write message setup
screen. See Table 5.E for descriptions of the message configuration data.
Figure 5.11 RSLogix 5000 Example Modbus RTU Master Write Message Setup Screen
In this example, Logic Command and Reference are being written to a
PowerFlex 70 drive. The CH3_MSG1_REQ array (14 bytes = 7 words)
contains the command data where:
A Destination element is not needed for a write message because no data
is returned.
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
CH3_MSG1_REQ [0] 15 PowerFlex 70 node address
CH3_MSG1_REQ [1] 16 Function Code – Write Multiple Registers
CH3_MSG1_REQ [2] 0 Starting Register Address (40001)
CH3_MSG1_REQ [3] 3 Number of registers to write
CH3_MSG1_REQ [4] 18 Value for 40001 – Logic Command word
CH3_MSG1_REQ [5] 0 Value for 40002 – not used
CH3_MSG1_REQ [6] 8192 Value for 40003 – Reference word