Distech Controls ECLYPSE APEX, Руководство пользователя

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157 ECLYPSE APEX
Controller Typical Data Bus Connection Terminals
Inverting Non-inverting Reference
Common identification labels
for Modbus RTU data bus
polarity by other
Manufacturers D0 D1 SC, C, or C
A or A’ B or B’ Common
Data – Data + Data 0V
Table 28: Common Identification Labels for Modbus RTU Data Bus Polarity for other Manufacturers
When interfacing with Modbus RTU devices from other manufacturers, refer to the documentation provided with the
device to correctly wire the device.
Maximum Number of Modbus RTU Devices on a Data
Bus Segment and Baud Rate
The number of Modbus devices supported by an ECY Series Controller is software limited according
to the controller model purchased. See the controller’s datasheet for more information. For ECY Se-
ries Controller models that are not software limited, the controller can support a combined maximum of
32 Modbus RTU and Modbus TCP devices.
Data Bus Segment Addressing Range for Modbus RTU Devices
The Modbus RTU device address range is 1 to 254. Address 0 is used to broadcast messages to all
slave devices and write only. When address 0 is used to broadcast a message, there is no confirma-
tion that the message was properly received by any slave device.
However, it is recommended that any given data bus segment have no more than 50 devices, when a
baud rate of 19 200 or higher is used for the Modbus RTU Data Bus. A repeater counts as a device on
each data bus segment to which it is connected.
Baud Rate
Most devices will have a range of baud rate settings and possibly an AUTO setting that detects the
baud rate of other devices transmitting on the data bus and adjusts the baud rate of the device accord-
ingly. Typical baud rates are 9600, 19 200, 38 400, and 76 800. The baud rate setting determines the
rate at which data is sent on the Modbus RTU data bus.
All devices on the data bus must be set to the same baud rate. Therefore, the chosen baud rate must
be supported by all devices connected to the data bus.
The recommended baud rate is 38 400.
We recommend that you:
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Set the baud rate of two controllers on a Modbus RTU Data Bus Segment to the same baud rate
to provide failover protection.
For example, set the baud rate of the ECY Series Controller (if equipped) and one other controller
to 38 400 baud. If the ECY Series Controller becomes unavailable and there is a power cycle, the
controller will set the baud rate for the Modbus RTU Data Bus.
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Set all other devices to automatically detect the baud rate, if this option is available.
Modbus RTU Communication Data Bus Fundamentals