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,
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 150Ω termination resistor (position "END").
3-POSITION SLIDE SWITCH
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
Controllers located on either end of bus should have
In small bus networks, a min. of one and a max. of
two controllers should have this setting.
All other controllers (not set to "END" or "BIAS") on
bus should have this setting (which is the default).
EAGLEHAWK CONTROLLER – INSTALLATION & COMMISSIONING INSTRUCTIONS
Fig. 11. RS485-1 three-position slide switch setting MID
Fig. 12. RS485-1 three-position slide switch setting BIAS
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