EIA-485 NETWORK
The EIA-485 network ports are used to accommodate serial network protocols that utilize 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 J2 and J3. Each
terminal has a connection for Network Positive (N+), Network Negative (N-), and Signal Ground Reference Wire
(SG, commonly used for serial networks that utilize a reference wire for electrical stability).
The Matrix Area Controller should be installed at an electrical end of the EIA-485 network. Avoid network
topologies where the network is “t-tapped” or “starred”.
CONNECTING 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 485 network wire to a reliable earth ground.
N+
N-
Figure 1-8 MS/TP Network Connection
NETWORK TERMINATION AND BIASING
Adjacent to each EIA-485 port is a two-position switch block, which applies termination and biasing to your
485 network. To enable either termination (TERM) or biasing (BIAS), configure the respective switch towards
the ON (Up) 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.
Figure 1-9 Termination and Biasing Switches and LED Indicators
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