Communications wiring
RTU Open v5
CARRIER CORPORATION ©2019
Integration Guide
All rights reserved
4
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
Unused
Comm
Option port
Protocol
Baud rate
8
7
6
5
4
3
2
1
BACnet MS/TP
(Default)
Master N/A
Off
Off
Off
On Off Select Baud
Select Baud
BACnet ARC156
N/A
Off
Off
Off
Off Off N/A
N/A
Modbus
Slave
N/A
Off
Off
On
On Off Select Baud
Select Baud
N2
Slave
N/A
Off
Off
Off
On On Off
Off
Lonworks
N/A
On
On
Off
On Off Off
On
Baud DIP switch settings
Baud Rate
DIP switch 2
DIP switch 1
9,600 bps
Off
Off
19.2 kbps
On
Off
Communications wiring
