EAGLEHAWK CONTROLLER – INSTALLATION & COMMISSIONING INSTRUCTIONS
7
EN1Z-1005GE51
R0216
RS485 Interfaces
General
The EAGLEHAWK controller features two RS485 interfaces:
RS485-1 (consisting of push-in terminals 24 [GND-1], 25,
and 26) is isolated and can be used for any RS485-based
communication protocol available within Niagara
Ecosystems, e.g.: Panel Bus, BACnet MS/TP, etc.
RS485-2 (consisting of push-in terminals 29, 30, and 31
[GND-2]) is non-isolated (i.e. GND-2 is internally con-
nected with terminal 1 [24V~0]) and can be used for any
RS485-based communication protocol available within
Niagara Ecosystems, e.g.: Panel Bus, BACnet MS/TP,
etc.
RS485-1 Bias and Termination Resistors
RS485-1 is equipped with a three-position slide switch which
can be used to switch its bias resistors OFF (position “MID” –
this is the default), ON (position “BIAS”), and ON with an
additional 150
Ω
termination resistor (position “END”).
J1
J8
RS485-1
3-POSITION SLIDE SWITCH
END
BI
A
S
MID
EN
D
BI
A
S
MI
D
Fig. 10. RS485-1 three-position slide switch
The recommended slide switch setting depends upon the
location and usage of the given EAGLEHAWK – see Fig. 11
through Fig. 13 and Table 5; it also depends upon the
selected communication protocol (BACnet MS/TP, Panel Bus,
or Modbus RTU Master communication, respectively).
Table 5. Recommended slide switch settings
setting
remarks
END
Controllers located on either end of bus should have
this setting.
BIAS
In small bus networks, a min. of one and a max. of
two controllers should have this setting.
MID
All other controllers (not set to “END” or “BIAS”) on
bus should have this setting (which is the default).
47 kOHM
47 kOHM
+5V
ISO
GND-1
RS485-1 (+)
RS485-1 (-)
25
26
MID (DEFAULT)
EN
D
BIAS
MI
D
Fig. 11. RS485-1 three-position slide switch setting MID
550 OHM
550 OHM
+5V
ISO
GND-1
RS485-1 (+)
RS485-1 (-)
25
26
BIAS
EN
D
BI
A
S
MI
D
Fig. 12. RS485-1 three-position slide switch setting BIAS
550 OHM
150 OHM
550 OHM
+5V
ISO
GND-1
RS485-1 (+)
RS485-1 (-)
25
26
END
END
BI
AS
MID
Fig. 13. RS485-1 three-position slide switch setting END
NOTE:
All terminals are protected (up to 24 Vac) against
short-circuiting and incorrect wiring – except when
the 3-position slide switch is set to “END,” in which
case the terminals of the RS485-1 bus (24, 25, and
26) have no such protection. Higher voltages may
damage the device.
NOTE:
According to BACnet standards, a minimum of one
and a maximum of two BACnet devices must have
its/their bias resistors switched ON. In the case of
the RS485-1 interface of the EAGLEHAWK, setting
its slide switch to either "BIAS" or "END" fulfills this
requirement.
