9.1.4 Modbus TCP Client
The DXM can operate as a Modbus TCP client on Ethernet. Users may define up to five socket connections for Modbus TCP
server devices to read Modbus register data over Ethernet. Use the DXM Configuration Software to define and configure
Modbus TCP client communications with other Modbus TCP servers.
9.2 Modbus Register Summary
9.2.1 DXM Modbus Registers
The DXM may have up to four internal Modbus slave devices.
All Modbus registers are defined as 16-bit Modbus Holding Registers. When connecting external Modbus slave devices, only
use Modbus slave IDs 2 through 198. The local registers, the I/O base, and the LCD slave IDs are fixed, but the internal radio
slave ID can be changed if needed.
Table 16: DXM Internal Modbus Slave IDs (factory default)
Modbus Slave ID
Device
1
DX80 Performance Gateway or MultiHop ISM Radio—MultiHop wireless devices connected to the internal MultiHop radio
should be assigned Modbus Slave addresses starting at 11.
199
Local Registers—Internal storage registers of the DXM
200
I/O Base Board—All data and parameters for each input or output of the DXM.
201
LCD Display—The user has access to the LED indicators on the DXM.
9.2.2 Modbus Registers for the MultiHop Radio Board Module
The DX80 MultiHop master radio is a tree-based architecture device that allows for repeater radios to extend the wireless
network. Each device in a MultiHop network is a Modbus device with a unique Modbus ID.
Modbus registers in a MultiHop network are contained within each individual radio device. To obtain Modbus register data
from a MultiHop device, configure the DXM to access each device across the wireless network as an individual Modbus slave
device.
Table 17: Example MultiHop Modbus registers with generic devices.
MulitHop Device
Slave ID
Modbus Registers
DXM Master radio
1
none
Slave radio
11
Modbus register 1–16 are inputs, 501–516 are outputs
Repeater radio
12
Modbus register 1–16 are inputs, 501–516 are outputs
Slave radio
15
Modbus register 1–16 are inputs, 501–516 are outputs
9.2.3 Modbus Registers for the Performance Gateway Radio Module
The DX80 Performance Gateway is a star-based architecture device that contains all the Modbus registers for the wireless
network within the Gateway. To access any input or output values within the entire wireless network, read the appropriate
Modbus register from Gateway.
There are 16 Modbus registers allocated for each device in the wireless network. The first 16 registers (1–16) are allocated
for the Gateway, the next 16 (17–32) are allocated for Node 1, the next 16 (33–48) are allocated for Node 2 and so forth.
There are no inputs or outputs on the DXM embedded Gateway but the Modbus registers are still allocated for them.
Although only seven Nodes are listed in the table, the Modbus register numbering continues for as many Nodes as are in the
network. For example, the register number for Node 10, I/O point 15 , is 175. Calculate the Modbus register number for each
device using the equation:
Register Number = I/O# + (Node# × 16)
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DXM100-Bx and DXM1000-Bx Wireless Controllers
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