RuggedCom RuggedMC RMC30, User Manual

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Appendix D. ModBus Management Support and Memory
Map
ROS® v3.11User Guide 125 RMC30
Appendix D. ModBus Management Support and
Memory Map
ModBus management support in RuggedCom devices provides a simple interface for
retrieving basic status information. ModBus support simplifies the job of SCADA (Supervisory
Control And Data Acquisition) system integrators by providing familiar protocol for the retrieval
of RuggedCom device information. ModBus provides mostly read-only status information, but
there are also a few writable registers for operator commands.
The ModBus protocol PDU (Protocol Data Unit) format is as follows:
Function Code Data
RuggedCom devices support the following ModBus function codes for device management
through ModBus:
1. Read Input Registers or Read Holding Registers – 0x04 or 0x03, for which the Modbus
PDU looks 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 = the number 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 = the number 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)
Note that as RuggedCom devices have a variable number of ports, not all registers and bits
apply to all products.