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February 02, 2024

DXM1200-X2 Controller Instruction Manual

Assigning Modbus IDs

Set the DXM ID from the LCD menu under System

›

DXM Server ID. The DXM Controller can have any unique ID.

DXM Client Configuration

—When the

DXM Controller operates as a Modbus client device, use the DXM Configuration

Software to configure read or write operations of the DXM Modbus network. The DXM Controller communicates with all
internal and external peripheral devices using the external Modbus bus RS-485.

There are four internal Modbus server devices that are configured from the factory with Modbus IDs. Assign IDs of 2 through
10 to Modbus server devices that are physically wired to the DXM Controller. Assign IDs or 11 through 60 to wireless servers
within the MultiHop network.

Do not assign an ID of greater than 10 to Modbus server devices that are physically wired using the RS-485 port if there is an
internal MultiHop ISM radio in the DXM Controller. The MultiHop ISM radio attempts to send any Modbus data intended for

IDs 11–60 across the radio network, which conflicts with wired server devices if the IDs overlap. The MultiHop client radio can
be changed from the factory default of 11–60 Modbus IDs if more hardwired servers are required.

Modbus Operation

All Modbus transactions are managed by a central Modbus engine. If there are Modbus messages intended for a Modbus
server that doesn't exist, the Modbus engine waits for a response until the timeout period is expired. This slows down the
Modbus polling loop for read and write operations.

For this reason, verify all Modbus read and write operations are intended for Modbus server devices that are in the network. If
a Modbus server is not in the network, either a wired or wireless device, the operation of the LCD menu system can be
compromised. Operations like Binding, Site Survey, or accessing the ISM menu may be slower. This is because all internal
devices (such as the ISM radio, LCD, etc) of the DXM Controller are also Modbus servers.

Wireless and Wired Devices

Wireless DX80 Performance Gateway

—The DX80 Performance Gateway architecture is a star architecture in which all

Nodes in the system send their data back to the Gateway. The host can access the entire network data from the Gateway,
which is Modbus ID 1. Because the DXM Controller will not be sending any Modbus messages across the wireless link, the
timeout parameter can be set low (less than 1 second) and the device is treated like a directly connected device.

MultiHop Client

—The MultiHop client radio forms a wireless tree network using repeaters and server devices. Each device in

a MultiHop network must be assigned a unique Modbus ID and is accessed as a separate device.

For the DXM Controller to talk with a MultiHop device in the wireless network, the client MultiHop device interrogates every
message on the RS-485 bus. If they are within the wireless device range (IDs 11 though 60), the message is sent across the
wireless network. To change this range, the user must adjust the offset and range setting in the MultiHop client radio (Modbus
ID 1). Modbus register 6502 holds the Modbus offset, default 11. Modbus register 6503 holds the number of Modbus servers
allowed (maximum of 100).

Modbus IDs for wireless and wired devices

Modbus ID

Description

Allocated for the internal ISM radio device, either a DX80 Performance Gateway or MultiHop Client

2–10

IDs available for direct-connected Modbus server devices to the client RS485 port (M+ , M-)

11–60

Allocated for wireless MultiHop radio network devices. If there is not an internal MultiHop in the DXM Controller, these server
addresses are available to use for directly connected devices.

61–198

Available to users for direct-connected Modbus server devices or the expansion of the wireless network server IDs to go past 50
wireless devices.

199

Allocated for internal Local Register

201

Allocated for the LCD display board, the user can read/write LEDs.