Quatech RS-485 user manual Used when external handshaking or

		Used when external handshaking or
		clocking signals are not available.
		RTS routed to AUXOUT, AUXIN
Modem Control		routed to CTS, and TCLK routed to
		RCLK. Used when RTS/CTS
		handshaking is required.
		RTS routed to CTS, AUXIN routed to
		RCLK, and TCLK routed to AUXOUT.
Clocks		Used to connect ports transmitting at
		different baud rates. In order to
		function, all ports must have and use
		this feature.
	Receive Control
		Receivers are always enabled. In a Half
Always Receive		Duplex mode, you will receive what you
		transmit (sometimes called echo).
		Receivers are only enabled when not
When NOT Tranmitting		transmitting. In a Half Duplex mode,
		you will not receive what you transmit.
RS-422/485 Duplex Mode
		Transmitters and receivers are always
Full Duplex		enabled; ports can send and receive
		simultaneously. Used in four-wire
		communication.
Half Duplex using RTS		RTS is set to enable the transmitters.
		Used in two-wire communication.
Half Duplex using DTR		DTR is set to enable the transmitters.
		Used in two-wire communication
		Hardware automatically enables the
		transmitters when transmitting.
Auto Toggle		Transmitters will turn off three bit-times
		after the last stop bit of the last
		character, regardless of baud rate. Used
		in two-wire communication.

8.To summarize the RS-422/485 output drivers enable options: The DSC-200/300’s ports may be configured for either full duplex or half duplex operation with this option. The default setting is the RS-422/485 ports are configured for full duplex operation with the RS-422/485 output drivers always enabled. In half duplex mode, the RS-422/485 transmitter may be enabled and disabled via the RTS (request to send) or DTR (data terminal ready) signals, or in auto-toggle mode, set to enable only when data is being transmitted. Both RTS and DTR are controlled through the Modem Control Register of the 16550.

Quatech DSC-200/300 User's Manual 28