Rockwell Automation 1769-SM2 Compact I/O DSI/Modbus Communication Module - Manual (Page 79)

Understanding Explicit Messaging 5-15
RSLogix 5000 Modbus RTU Master Read Message Example
Figure 5.12 shows an example Modbus RTU Master read message setup
screen. See Table 5.E for descriptions of the message configuration data.
Figure 5.12 RSLogix 5000 Example Modbus RTU Master Read Message Setup Screen
In this example, Logic Status and Feedback are being read from a
PowerFlex 70 drive. The CH3_MSG2_REQ array (8 bytes = 4 words)
contains the command data where:
The CH3_MSG2_RESP array contains the response data where:
For additional information about Modbus RTU read messages for
PowerFlex 7-Class drives, refer to the 20-COMM-H Adapter User
Manual, publication 20COMM-UM009.
Data Word Example Value Description
CH3_MSG2_REQ [0] 15 PowerFlex 70 node address
CH3_MSG2_REQ [1] 4 Function Code – Read Input Registers
CH3_MSG2_REQ [2] 0 Starting Register Address (30001)
CH3_MSG2_REQ [3] 3 Number of registers to read
Data Word Example Value Description
CH3_MSG2_RESP [0] 3855 Value for 30001 – Logic Status word
CH3_MSG2_RESP [1] 0 Value for 30002 – not used
CH3_MSG2_RESP [2] 8192 Value for 30003 – Feedback word