Issue
What are the jumpers labeled TERM3 through TERM6 used for on the I/A Series R2 UNC-520 and G3 ENC-520?
Environment
I/A Series R2 UNC-520
I/A Series G3 ENC-520
Cause
Hardware communications bus bias resistor pairs.
Resolution
The UNC-520-2 and ENC-520-2 hardware circuitry includes a set of bias resistors that can be individually enabled as pairs, one set for each of the four RS-485 ports. These jumpers change the default bias resistor set for each RS-485 COM port from a device level bias to a “pull-apart” level bias. These are NOT end-of-line terminators. In most cases, the bias resistors should remain enabled. Reference technical bulletin (TB06-09) for more details.