Quatech QSP-200/300 user manual Options

3 Options:

Half Duplex

-RTS

-DTR

MUX

16C550

	Data Out
RS-422/485		+
Driver		-

Active Low

Output Enable

Aux Out

Full Duplex

RS-422/485

+

Driver

-

NOTE: One of these three options must be selected via software configuration. Full duplex operation is the default mode.

Figure 8. RS-422/485 Driver Enable Options

If RTS is selected as the signal to enable the output drivers, setting 'bit 1' of the Modem Control Register (to logic '1') will enable the output drivers and clearing 'bit 1' of the Modem Control Register (to logic '0') will force the outputs into a high impedance state.

Similarly, if DTR is chosen as the signal to enable the output drivers setting 'bit 0' of the Modem Control Register (to logic '1') will enable the output drivers and clearing 'bit 0' of the Modem Control Register (to logic '0') will force the outputs into a high impedance state.

Selection of half duplex mode operation is dependent upon the configuration software and/or the operating system used. Each of these,

however, ultimately control the half duplex mode by accessing the PCMCIA Configuration Register on the QSP-200/300.

CAUTION:

When operating in half duplex mode, the transmitter output drivers must be disabled before receiving and information. Failure to do so will result in two output drivers being connected together which may cause damage to the adapter, the computer, and/or the peripheral equipment.

QSP-200/300 User's Manual 39