Quatech QSP-200/300 - Manual (Page 24)

RTS Controlled o2
DTR Controlled o1
Figure 3. DOS Client Output Driver Options.
H instructs the client driver to enable the RTS-CTS modem control handshake. When
modem control handshaking in enabled, the 16C550 UART’s RTS and CTS signals
are connected to the RS-422/485 auxiliary channel (AuxOut and AuxIn). The
auxiliary channel may then be used for handshaking between a DSP-200/300
RS-422/485 port and a peripheral device. When modem control handshaking is
disabled, the RTS and CTS signals from the 16C550 UART are looped back to each
other. If this option is omitted, the default setting is RTS-CTS modem control
handshake disabled. See the Hardware Information section for more information.
U instructs the Client Driver to disable the QSP-200/300's interrupt status register and
enable the Scratchpad registers of the individual UARTs. This option is only
required in very rare cases where an application program requires access to the
UART's Scratchpad register. If this option is omitted, the QSP-200/300's interrupt
status register is enabled and the UARTs' Scratchpad registers are disabled.
QSP-200/300 User's Manual 18