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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. 49 and 50 for
protocol switch settings and address switches. The 3rd
party connection to the RTU Open is through plug J19.
See Fig. 51 for wiring.
NOTE: Power must be cycled after changing the SW1--3
switch settings.
Contact your Bryant applications engineer for more
detailed information on protocols, 3rd party wiring, and
networking.
SW3 Protocol Selection
PROTOCOL DS8 DS7 DS6 DS5 DS4 DS3 DS2 DS1
BACnet MS/TP
(Master)
Unused OFF OFF OFF ON OFF Se lect Baud Select Baud
Modbus
(Slave)
Unused OFF OFF ON ON OFF Se lect Baud Select Baud
N2
(Slave)
Unused OFF OFF OFF ON ON OFF OFF
LonWorks Unused ON ON OFF ON OFF OFF OFF
NOTE:
DS = Dip Switch
BACnet MS/TP SW3 example shown
Baud Rate Selections
BAUD RATE DS2 DS1
9600 OFF OFF
19,200 ON OFF
38,400 OFF ON
76,800 ON ON
C07166
Fig. 49 -- RTU Open SW3 Dip Switch Settings
C10815
Fig. 50 -- RTU Open Address Switches
C10816
Fig. 51 -- Network Wiring
581J