Rockwell Automation 2080-L70E-24QBB - Appendix A Modbus Mapping for Micro800; Modbus Mapping; Mapping Address Space and Supported Data Types

Rockwell Automation Publication 2080-UM002N-EN-E - November 2022 261
Appendix A
Modbus Mapping for Micro800
Modbus Mapping All Micro800 controllers (except the Micro810 12-point models) support Modbus RTU over a
serial port through the embedded, non-isolated serial port. The 2080-SERIALISOL isolated
serial port plug-in module also supports Modbus RTU. Both Modbus RTU master and slave are
supported. Although performance may be affected by the program scan time, the 48-point
controllers can support up to six serial ports (one embedded and five plug-ins), and so
consequently, six separate Modbus networks.
In addition, the Micro850 and Micro870 controller support Modbus TCP Client/Server through
the Ethernet port.
Endian Configuration
Modbus protocol is big-endian in that the most significant byte of a 16-bit word is transmitted
first. Micro800 is also big-endian, so byte ordering does not have to be reversed. For Micro800
data types larger than 16 bits (for example, DINT, LINT, REAL, LREAL), multiple Modbus
addresses may be required but the most significant byte is always first.
Mapping Address Space and Supported Data Types
Since Micro800 uses symbolic variable names instead of physical memory addresses, a
mapping from symbolic Variable name to physical Modbus addressing is supported in
Connected Components Workbench software, for example, InputSensorA is mapped to Modbus
address 100001.
By default Micro800 follows the six-digit addressing specified in the latest Modbus
specification. For convenience, conceptually the Modbus address is mapped with the following
address ranges. The Connected Components Workbench mapping screen follows this
convention.
Table 64 - Mapping Table
Variable Data Type
0 - Coils
000001…065536
1 - Discrete Inputs
100001…165536
3 - Input Registers
300001…365536
4 - Holding Registers
400001…465536
Supported
Modbus Address
Used
Supported
Modbus Address
Used
Supported
Modbus Address
Used
Supported
Modbus Address
Used
BOOL Y 1 Y 1
SINT Y 8 Y 8
BYTE Y 8 Y 8
USINT Y 8 Y 8
INT Y 16 Y 16 Y 1 Y 1
UINT Y 16 Y 16 Y 1 Y 1
WORD Y16 Y16 Y1 Y1
REAL Y32 Y32 Y2 Y2
DINT Y32 Y32 Y2 Y2
UDINT Y 32 Y 32 Y 2 Y 2
DWORD Y 32 Y 32 Y 2 Y 2
LWORD Y 64 Y 64 Y 4 Y 4