Perle Systems 5500152-23 manual UltraPort Serial Adaptors User Guide, Page

EIA-485 HDX Local Echo: Local echo by default is on. This parameter applies only to EIA-485 half duplex mode. All characters will be echoed to the user and transmitted across the serial ports. Some EIA-485 applications require local echo to be enable in order to monitor the loopback data to determine that line contention has occurred. If your application cannot handle loopback data the local echo should be disabled.

EIA-485 TX Driver Control: The default for this field is AUTO. When Auto is set the UltraPort SI will automatically detect the beginning and the ending of data being transmitted in order to enable and disable the transmit line. When the field is set to RTS it is the host application’s responsibility to enable and disable the transmit line via the RTS handshake line when it wants to send data.

Auto EIA-485 Bit Delay: By default this field is set to 0 delay. This field is only applicable if you have configured EIA-485 TX Driver Control to AUTO. Values for this field are 0 through 15 bits.

Note

The port must be closed and then opened for the new parameters to take effect.

UltraPort Serial Adaptors User Guide	Chapter 2 Installing drivers and host cards
Installing under Windows 2000/XP/Server 2003/Vista/Server 2008
Page 41