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Communications wiring
Communications wiring
Protocol overview
Protocols are the communication languages spoken by the control devices. The main purpose of a protocol is to
communicate information in the most efficient method possible. Different protocols exist to provide specific
information for different applications.
In the BAS, many different protocols might be used, depending on manufacturer. Different protocols do not
change the function of the controller, but they typically require the owner to change systems or components in
order to change from one protocol to another. communicates different types of protocols.
The RTU Open can communicate 1 of 5 different protocols:
BACnet MS/TP (page 5)
BACnet ARC156 (page 9)
Modbus (page 11)
Johnson N2 (page 14)
LonWorks (page 16)
The default setting is BACnet MS/TP. You set the protocol and baud rate using the SW3 DIP switches. The rotary
switches MSB (SW1) and LSB (SW2) set the board's network address. See table below for specific switch settings.
The third party connects to the controller through port J19 for BACnet MS/TP, BACnet ARC156, Modbus, and N2,
and through J15 for the LonWorks Option Card.
NOTE You must cycle power after changing the rotary switches or after connecting the LonWorks Option Card to
J15.
SW3 DIP switch settings
BACnet MS/TP
(Default)
BACnet ARC156
Modbus
N2
Lonworks
Baud DIP switch settings
Baud Rate
9,600 bps
19.2 kbps
RTU Open v5
Integration Guide
Unused
Comm
Option port
8
7
Master N/A
Off
N/A
Off
Slave
N/A
Off
Slave
N/A
Off
N/A
On
DIP switch 2
Off
On
Protocol
6
5
4
3
Off
Off
On
Off
Off
Off
Off
Off
Off
On
On
Off
Off
Off
On
On
On
Off
On
Off
DIP switch 1
Off
Off
4
Baud rate
2
1
Select Baud
Select Baud
N/A
N/A
Select Baud
Select Baud
Off
Off
Off
On
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