InteliMains 210 Global Guide
38
On board RS485 description
Balancing resistors
The transmission bus into the RS-485 port enters an indeterminate state when it is not being transmitted to. This
indeterminate state can cause the receivers to receive invalid data bits from the noise picked up on the cable.
To prevent these data bits, you should force the transmission line into a known state. By installing two 620 Ohm
balancing resistors at one node on the transmission line, you can create a voltage divider that forces the voltage
between the differential pair to be less than 200 mili-Volts, the threshold for the receiver. You should install
these resistors on only one node. The figure below shows a transmission line using bias resistors. Balancíng
resistors are placed directly on the PCB of controller. Use jumpers PULL UP/PULL DOWN to connect the
balancing resistors.
Image 4.15 Balancing resistors
Image 4.16 RS485 on board