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Communication Wiring- Protocols
General
Protocols are the communication languages spoken by
control devices. The main purpose of a protocol is to
communicate information in the most efficient method
possible. Different protocols exist to provide different
kinds of information for different applications. In the BAS
application, many different protocols are used, depending
on manufacturer. Protocols do not change the function of
a controller; just make the front end user different.
The RTU Open can be set to communicate on four
different protocols: BACnet, Modbus, N2, and LonWorks.
Switch 3 (SW3) on the board is used to set protocol and
baud rate. Switches 1 and 2 (SW1 and SW2) are used to
set the board's network address. See Fig. 11 and 12 for
protocol switch settings and address switches. The 3rd
party connection to the RTU Open is through plug J19.
See Fig. 13 for wiring. Contact Bryant applications
engineering for more detailed information on protocols,
3rd party wiring, and networking.
Fig. 10 - Enthalpy Switch and Sensor Wiring
10
NOTE: Power must be cycled after changing the SW1- 3
switch settings.
R
BACnet
MS/TP
BACnet Master Slave/Token Passing (MS/TP) is used for
communicating
BACnet
BACnet- only controllers. This is the default Bryant
communications protocol. Each RTU Open module acts as
an MS/TP Master. The speed of an MS/TP network can
range from 9600 to 76.8K baud. Physical Addresses can
be set from 01 to 99.
C10821
over
a
sub- network
of
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