To use auto direction control for RS-485, the port must be configured in the Windows® Device Manager.
Open the Windows® Device Manager.
Right-click the port that RS-485 is assigned to. Assigned ports vary depending on
configured optional interfaces. Refer to Before Using Serial Interface Options (the example below
uses COM5 and COM6).
Select Properties and open the Port Settings tab.
Select the RS-485 check box.
Turn Around Time specifies
the length of time (data bit time) after transmission of communication
data is complete, until the system changes to a state where it can
receive communication data. After the specified time elapses, the
system is in the state to receive data. Set the data bit time if used
in a long-distance communication environment where propagation delay
needs to be considered. The default value is 0.