Quatech RS-422 - Manual (Page 8)

2.2 Signal Connections
The DSCLP-200/300 provides each of two serial ports with four differential
signal pairs: TxD, RxD, AUXOUT, and AUXIN. TxD and RxD are always present at
the connector. The AUXOUT and AUXIN signals can be used to support RTS/CTS
handshaking, external clocking, or external signal loopback. The factory default
configuration, as shown in Figure 2, is a loopback of AUXOUT to AUXIN at the
connector, with RTS and CTS looped back on the board. There is an extensive
discussion of this topic starting on page 19.
2.3 Full-duplex/Half-duplex Operation
The DTR or RTS modem control output of the UART can be used to enable
and disable the transmit drivers. The inverse of these signals can also be used to enable
and disable the receivers. These options are selectable per channel. The factory
default, as shown in Figure 2, is for both the drivers and receivers of both channels to
be continuously enabled. Two spare jumpers are installed in neutral positions. For
details, refer to page 22.
The DSCLP-200/300 is shipped from the factory with each channel configured
with No jumpers on J10-23. The following conditions occur: CTS=AUXIN,
AUXOUT=RTS, RCLK=TCLK, TXEN=1 AND RXEN=1.
Jumpers J10-J23 define the options for this card:
DSCLP-200/300 User's Manual 3