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 |