Quatech SSCF-200 User manual - page 10
Quatech CompactFlash Card User’s Manual
SSCF-200/300
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6.4 RS-422 OPERATION
Generally, in RS-422 systems, all 8 signal lines from the DB9 connector are used. Thus 4 twisted
pair cables are used, one pair for each of the 4 signals TXD, RXD, RTS and CTS. The RS-422
arrangement allows data to be transmitted and received simultaneously since each signal has its
own twisted pair.
6.5 RS-485 OPERATION
The SSCF-200/300 can be used for both half-duplex (one twisted pair) and full-duplex (two twisted
pairs) arrangements, however for half-duplex mode, the link between the TXD and RXD signals
must be made externally on the DB9 connector. Also, it should be noted that the transmitted
characters will always be received in this mode. The RXD receiver is not disabled during
transmission.
The handshaking signals RTS and CTS, although driven by the card, are usually not connected to
another node. However, if required by the application software, to force the CTS signal input on the
SSCF-200/300 true, the RTS signals must be looped back to the CTS inputs.