I need to add theses resistors when using RS485 modbus or is it built-in?
The CR1000X does not contain termination resistors on the RS485 A- and B+ terminals. We do offer the resistive ground (RG) terminal on the CR1000X that is 100 ohm resistance to ground to terminate the RS485 ground. We have found that termination resistors are rarely needed. If you need termination resistors to eliminate reflections then realize the tradeoff is that power requirements will increase.