CMD-standalone controllers have the ability to communicate over a RS-485 serial communication interface with the motion core using an ASCII protocol.  This allows for a simple, half-duplex, bi-direction multi-drop network using a single twisted pair.


Below is the detailed schematic of the RS-485 communication line input.

Schematic:


Parameter

Value

Transceiver

3.3 V RS-485/RS-422 transceiver, half duplex

Bus voltage

−7 V to +12 V (common-mode range)

Termination

120 Ω AC termination (120 Ω in series with 1 nF) permanently fitted; not switchable

Fail-safe bias

None on the board; bias the bus at one node if required

Protection

10 Ω series resistors, TVS diodes on both lines

Isolation

None: referenced to logic ground

Notes:

More information about the RS485 input is available in the Serial Communication section of the Commander Theory of Operation manual.