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Appendix E – ModBus Management Support and Memory Ma
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RS400 267 ROS™ v3.5
Appendix E – ModBus Management Support and
Memory Map
ModBus management support in RuggedCom devices provides the user with a simple interface
with basic status information. Support for this protocol simplifies the job of SCADA System
integrators who can now easily use this feature to retrieve basic info from RuggedCom devices
via a familiar protocol. Predominantly read-only status information is provided though a few
writable registers exist to provide operator commands.
The PDU format defined for the ModBus protocol is
Function Code Data
The following ModBus function codes are supported by RuggedCom for device management
through ModBus:
(1) Read Input Registers or Read Holding Registers – 0x04 or 0x03 for which the Modbus PDU
would look like:
Request
Function code 1 Byte
0x04(0x03)
Starting Address 2 Bytes 0x0000 to 0xFFFF
Number of Input Registers 2 Bytes 0x0001 to 0x007D
Response
Function code 1 Byte
0x04(0x03)
Byte Count 1 Byte 2 x N*
Input Registers N*X2 Bytes
*N = Quantity of Input Registers
(2) Write Multiple Registers – 0x10
Request
Function code 1 Byte
0x10
Starting Address 2 Bytes 0x0000 to 0xFFFF
Number of Registers 2 Bytes 0x0001 to 0x0079
Byte Count 1 Byte 2 x N*
Registers Value N* x 2 Bytes Value of the register
*N = Quantity of Input Registers
Response
Function code 1 Byte
0x10
Starting Address 2 Bytes 0x0000 to 0xFFFF
Number of Registers 2 Bytes 1 to 121 (0x79)