ProSoft Technology MVI56E-MCM/MCMXT - Manual (Page 41)

MVI56E-MCM ♦ ControlLogix Platform Configuration as a Modbus Master
Modbus Communication Module User Manual
ProSoft Technology, Inc. Page 41 of 199
June 18, 2014
Below is a definition that will help with your DevAddress configuration:
Function Codes 1, 5, or 15 DevAddress = Modbus address in device - 0001
 Example: Modbus address 0001 = DevAddress 0
 Modbus address 1378 = DevAddress 1377
Function Code 2 DevAddress = Modbus address in device - 100001
 Example: Modbus address 100001 = DevAddress 0
 Modbus address 100345 = DevAddress 344
Function Codes 3, 6, or 16 DevAddress = Modbus address in device - 400001
 Example: Modbus address 400001 = DevAddress 0
 Modbus address 400591 = DevAddress 590
Function Code 4 DevAddress = Modbus address in device - 300001
 Example: Modbus address 300001 = DevAddress 0
 Modbus address 304290 = DevAddress 4289
For example, our device listed above could show their addressing as follows.
To read the same parameter "Switch_Input_Status", you would still issue a
Function Code 4, and use a DevAddress of 512 decimal.
2.3 Master Command Examples
2.3.1 Read Holding Registers 4x (Modbus Function Code 3)
The 4x holding registers are used for Analog Values such as Pressure,
Temperature, Current, and so on. These are 16-bit register values, but they can
also store Floating-Point Data Handling (Modbus Master) (page 46). You can
also write to these Modbus addresses using Modbus Function Codes 6 or 16.
Below is a sample command to read Modbus addresses 40001 to 40010 of node
1 on the Modbus network.