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1. General Information
The Quatech, Inc. DS-200/300 provides two RS-422/RS-485 asynchronous serial
communication interfaces for IBM-compatible personal computer systems using
the 16-bit ISA (Industry Standard Architecture) expansion bus.
The DS-200/300's serial ports are implemented using 16550 or 16750 Universal
Asynchronous Receiver/Transmitters (UARTs). The 16550 UARTs enable the
DS-200/300 to transmit and receive data at a rate of up to 230.4 kbaud; the 16750
UARTs enable data rates of up to 921.6 kbaud. The data rate can be altered either
through hardware or software. The 16550 contains a 16-byte hardware buffer that
reduces processing overhead; the 16750 contains a 64-byte hardware buffer. To
use the 16550/16750's buffering capabilities, the software must be aware of the
UART's presence. Otherwise, it will act as a 16450 UART. The 16750 is
suggested for heavy multitasking environments and for applications involving
high data rates.
The DS-200/300 uses Quatech’s new Enhanced Serial Adapter design. This
allows the user to access higher data rates by either setting a jumper on the board
or by programming a special register. The register also allows the board to be
identified as a Quatech Enhanced Serial Adapter. This enables specially written
software to take advantage of the added features.
The DS-200/300 is highly flexible with respect to addressing and interrupt level
use. The serial ports are individually addressed and can be placed anywhere
within the range of 0000 hex to FFF8 hex at 0008 hex intervals. Available
interrupt levels include IRQ2 to IRQ7, IRQ10 to IRQ12, IRQ14, or IRQ15.
Both ports on the DS-200/300 can share one interrupt level or an interrupt level
can be shared with another Quatech adapter that supports interupt sharing. A
special Interrupt Status Register is provided to allow controlling software to
manage the shared interrupt level. The shared interrupt feature minimizes the
system resources consumed by the adapter.
In order to support the use of the shared interrupt feature and the higher data rates
of the DS-200/300, Quatech has developed device drivers for several popular
operating systems and environments. The sales department can be contacted for
details on current offerings.
DS-200/300 User's Manual 1-1