118 ECLYPSE APEX
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 BACnet MS/TP data bus.
At 9600 baud, the maximum number of devices is reduced to 25 due to the increased time it takes for token
passing between devices.
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 for Distech Controls’ devices is 38 400.
We recommend that you:
£ Set the baud rate of two controllers on a BACnet MS/TP 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
ECB controller will set the baud rate for the BACnet MS/TP Data Bus.
£ Set all other devices to automatically detect the baud rate, if this option is available.
Typical BACnet Device
NET+
NET-
Typical BACnet Device
NET+
NET-
Typical BACnet Device
NET+
NET-
Typical BACnet Device
NET+
NET-
EOL ON
EOL OFF
EOL OFF
EOL OFF
Data Bus: Shielded Twisted Pair Cable
Electrical
System
Ground
Baud: Auto (Factory Default) Baud: Auto (Factory Default) Baud: Auto (Factory Default) Baud: 38 400 Baud: 38 400
RS-485
-
+
S
ECLYPSE
END
EOL ON
Figure89: Setting the Baud rate on two Controllers on a BACnet MS/TP Data Bus Segment for Failover Protec-
tion
To set the baud rate for:
£ ECLYPSE Series Controllers, see Network MS/TP Ports.
£ ECB Series controllers, see the controller’s hardware installation guide or the Network Guide.
BACnet MS/TP Communication Data Bus Fundamentals
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