MVI56E-MCMR ♦ ControlLogix Platform Configuring the MVI56E-MCMR Module
Modbus Communication Module with Reduced Data Block User Manual
ProSoft Technology, Inc. Page 61 of 223
2.3.5 Other Modbus Addressing Schemes
While the above information will handle most devices, some device
manufacturers show their Modbus addressing differently.
The two most common schemes are six-digit addressing (400101, 301000, and
so on) and some devices show their addressing already as an offset address (the
address that actually goes out on the Modbus communication line). When
addresses are given as actual offset addresses, they are usually given as a
hexadecimal (base 16) number. This is an example.
Actual Values (Input Registers) Addresses: 0200 to 0E1F
Output Relay Status Flags
If your device manufacturer gives you addressing like this "Input Registers"
example above, then you will use Function Code 4 to convert the hexadecimal
value to a decimal equivalent value, and place the decimal value in the MB
ADDRESS IN DEVICE field. So for this example device, use Modbus Function = 4
(Input Registers) with a MB ADDRESS IN DEVICE of 512 decimal (200h) to read the
"Switch Input Status" value.
What if my slave shows addresses such as 400,001 or 301,345?
For 6-digit addressing, use the same function codes and configuration as shown
above, but subtract higher values; 100001 instead of 10001; 300001 instead of
30001; and 400001 instead of 40001.
Function Codes 1, 5, or 15 MB Address in Device = Modbus Coil address in
slave device - 000001
For Modbus Coil address 000001; MB Address in Device = 0
For Modbus Coil address 001378; MB Address in Device = 1377
Function Code 2 MB Address in Device = Modbus Input Status address in slave
device - 100001
For Modbus Input Status address 100001; MB Address in Device = 0
For Modbus Input Status address 100345; MB Address in Device = 344
Function Codes 3, 6, or 16 MB Address in Device = Modbus Holding Register
address in slave device - 400001
For Modbus Holding Register address 400001; MB Address in Device = 0
For Modbus Holding Register address 400591; MB Address in Device = 590
Function Code 4 MB Address in Device = Modbus Input Register address in
device - 300001
For Modbus Input Register address 300001; MB Address in Device = 0
For Modbus Input Register address 304290; MB Address in Device = 4289
For example:
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