Quatech RS-422 user manual Signal Connections, Full-duplex/Half-duplex Operation

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