Built-in bias resistors for CompactRIO controller RS485 ports?

[DR_redviking]

Are there built-in bias resistors on the RS-485 ports for the newer cRIO controllers?  Specifically, I'm looking at the 906x and 903x series of controllers with RS-485 ports.

I can't seem to find any mention of these in the controller datasheets or user manuals.

[Davidvilla87 · Accepted solution]

Hi gregopher,

The cRIOs doesn´t have bias resistors on the RS-485.  As you can see in the following document there are some interfaces that comes with bias resistors.

http://digital.ni.com/public.nsf/allkb/12BB6CD900B2D0EF862564980050F5A7

We have being told by an engineer:

"The reciever inputs have open- and short-circuit, fail-safe features that ensure that the receiver output is high when the inputs are open or shorted. During line-idle conditions,
when no driver on the bus is enabled, the voltage across a terminating resistance at the receiver decays to 0V. This feature eliminate the need for bias resistors"