Distech Controls ECLYPSE APEX, Руководство пользователя

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120 ECLYPSE APEX
£
EIA-485 data bus transmitters are tri-state devices. That is they can electrically transmit 1, 0, and
an idle state. When the transmitter is in the idle state, it is effectively off-line or disconnected from
the data bus. EOL terminations serve to bias (pull-down and pull-up) each data line/wire when the
lines are not being driven by any device. When an un-driven data bus is properly biased by the
EOL terminations to known voltages, this provides increased noise immunity on the data bus by
reducing the likelihood that induced electrical noise on the data bus is interpreted as actual data.
When to Use EOL Terminations
EOL terminations should only be enabled / installed on the two devices located at either end of the
data bus. All other devices must not have the EOL terminations enabled/installed.
Typical BACnet Device
First and last daisy-chained device:
- EOL Terminations are ENABLED
OR EOL resistor is installed
All other Devices:
- EOL Terminations are DISABLED
N
E
T+
N
E
T
-
Typical BACnet Device
N
E
T+
N
E
T
-
Typical BACnet Device
N
E
T+
N
E
T
-
Typical BACnet Device
N
E
T+
N
E
T
-
EOL ON EOL OFF EOL OFF EOL OFF
Data Bus: Shielded Twisted Pair Cable
Electrical
System
Ground
RS-485
- +
S
ECLYPSE
EOL ENABLED:
When the
ECLYPSE control-
ler is the first or
last daisy-chained
device, set the
external EOL
termination to END
END
EOL ON
Figure 90: EOL Terminations Must be Enabled at Both the First and Last Device on the Data Bus
Devices with built-in EOL terminations are factory-set with the EOL termination disabled by default.
The BACnet/IP to MS/TP Adapter does not have EOL Termination (and BACnet MS/TP Data Bus biasing) capabilities
to be used at the end of a BACnet MS/TP data bus. Instead, use the BACnet/IP to MS/TP Router for this application.
When to use EOL Terminations with BACnet MS/TP Thermostats
BACnet MS/TP thermostats support external EOL termination resistors only. When a BACnet MS/TP
thermostat is the first or last daisy-chained device, add a 120 Ohm resistor across the – and + BACnet
MS/TP data bus connections.
The BACnet MS/TP data bus must be biased. This bias can only be provided by built-in EOL termina-
tion resistors (ones set with jumpers or DIP switches – refer to the controller’s Hardware Installation
Guide for how to identify and set a controller’s built-in EOL terminations). If a BACnet MS/TP data bus
has a BACnet MS/TP thermostat at one end of the BACnet MS/TP data bus and an ECY Series Con-
troller at the other end, you must set the built-in EOL termination in the controller so that proper bias-
ing is provided to the BACnet MS/TP data bus.
RS-485
-
+ S
END / BIAS
EOL and
biasing ON
ECLYPSE
Typical
BACnet
Device
First and last daisy-chained device:
- EOL Terminations are ENABLED
at one end, and EOL resistor is
installed at other end.
All other Devices:
- EOL Terminations are DISABLED.
N
ET
+
N
ET
-
Typical
BACnet
Device
N
ET
+
N
ET
-
Typical
BACnet
Device
N
ET
+
N
ET
-
Typical
BACnet
Device
N
ET
+
N
ET
-
No Built-in EOL
Termination
Data Bus: Shielded Twisted Pair Cable
No Built-in EOL
Termination
No Built-in EOL
Termination
No Built-in EOL
Termination
EOL: Add a 120
Ohm resistor as
shown here
120
Ω
Electrical
System
Ground
EOL ENABLED: Use the
ECLYPSE controller as a
first or last daisy-chained
device: The external EOL
switch MUST be set to
END/BIAS (middle posi-
tion) to provide bias and
EOL termination to the
BACnet MS/TP Data Bus
Figure 91: Typical EOL Terminations with BACnet MSTP Thermostats with Biasing Provided by the Controller’s
Built-in EOL Termination set to ON
BACnet MS/TP Communication Data Bus Fundamentals