AspectFT-Nexus & AspectFT-Facility Installation Guide (1/02/2014)
1-9
1.4.2 EIA-485 N
ETWORKING
AspectFT-Nexus products support two EIA-485 network ports to accommodate connections to serial
network protocols using two-wire, shielded-twisted pair cabling - such as BACnet MS/TP, American Auto-
Matrix PUP, and Modbus RTU.
Terminals for EIA-485 network connections are located on the left side of the controller board and are
labeled
PORT 1
and
PORT 2
. Each terminal has a connection for Network Positive (N+) and Network
Negative (N-). Avoid network topologies where the network is “t-tapped” or “starred”.
1.4.2.1 C
ONNECTING
EIA-485
NETWORKS
Connect the serial network to the determined EIA-485 port. Be sure to maintain network polarity at all
times. Failure to do so can result in loss of network communications. For protection against ground loops
or noise, connect the drain wire of the EIA-485 network wire to one of the supplied enclosure studs located
within the enclosure panel.
1.4.2.2 N
ETWORK
T
ERMINATION
AND
B
IASING
Adjacent to each EIA-485 port are two switches, which apply termination and biasing to your
485 network. To enable either termination (TERM) or biasing (BIAS), configure the respective switch
towards the left position.
When applying termination, be certain that it is applied at both ends of your EIA-485 network at the two
end devices. In termination applications, biasing should also be enabled to ensure proper idle state
voltage.
NOTE
EIA-485 networking capabilities are available on
AspectFT-Nexus product variants. AspectFT-
Facility does not support terminations to serial
networks, nor can it be field upgraded to do so.