9 Additional Information
9.1 Working with Modbus Devices
The DXM has two physical RS-485 connections using Modbus RTU protocol.
The DXM can be a Modbus RTU master device to other slave devices and can be a Modbus slave device to another Modbus
RTU master. The DXM uses the primary RS-485 port (M+/M-) as a Modbus RTU master to control external slave devices. All
wired devices connected to the master RS-485 port must be slave devices.
Figure 43. Processor Modbus system overview
Processor Modbus
Control/Data
Local
Registers
ISM
Radio
Display
I/O Base
Board
Modbus
SID 199
Modbus
SID 1
Modbus
SID 201
Modbus
SID 200
Ethernet
Modbus RS-485
(slave port)
External
Modbus
Slaves (2-10)
Modbus RS-485
(master port)
The DXM has dual Modbus roles: a Modbus slave device and a Modbus master device. These run as separate processes.
The Modbus slave port can only access the DXM local registers. To operate as a Modbus slave device, the DXM needs to be
assigned a unique Modbus slave ID as it pertains to the host Modbus network. This slave ID is separate from the internal
Modbus slave IDs the DXM uses for its own Modbus network. The DXM Modbus slave ID is defined through the LCD menu.
Other Modbus slave port parameters are defined by using the configuration software.
The DXM operates the Modbus master port. Each device on the master port must be assigned a unique slave ID. There are
slave IDs that are reserved for internal devices in the DXM.
Table 14: 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.
9.1.1 Assigning Modbus Slave IDs
Assign the DXM Modbus Slave ID only if a Modbus master device is reading or writing the DXM Local Register data through
the Modbus RS-485 slave port (S+, S-).
Set the DXM Slave ID from the LCD menu under
System
>
DXM Slave ID
. The DXM can have any unique slave ID between
1 and 246, depending upon the host Modbus network. Other RS-485 slave port parameters are set in the configuration
software under the
Settings
>
General
tab.
DXM Master Configuration
—When the DXM operates as a Modbus master device, use the configuration software to
configure read or write operations of the DXM Modbus network. The DXM communicates with all internal and external
peripheral devices using the external Modbus bus RS-485 (M+, M-)
There are four internal Modbus slave devices that are configured from the factory with slave IDs. Assign slave IDs of 2
through 10 to Modbus slave devices that are physically wired to the DXM. Assign slave IDs or 11 through 60 to wireless
slaves within the MultiHop network.
Sure Cross
®
DXM100-Bx and DXM1000-Bx Wireless Controllers
www.bannerengineering.com - Tel: + 1 888 373 6767
65
