PC Serial Ports
Issue 1 January 1997
E-9
2.
For best performance with MERLIN LEGEND Reporter, choose a card which has
hardware support for high-speed communications.
The MERLIN LEGEND Communications System transmits call records to the
MERLIN LEGEND Reporter at a data rate of 9600 baud, and it relies on Windows to
manage the flow of data through your PC's serial port. Depending upon your
configuration, Windows may have problems maintaining high data rates through
traditional serial ports. In these situations, a serial port designed for high-speed
communications can eliminate such problems while providing a reduced load on the
microprocessor (thus increasing the performance of Windows during data transfers
relative to standard serial ports). In most cases, the price differential for such a card
is quite modest and a worthwhile investment.
Many serial port cards on the market (and most built-in serial ports) use either the
8250 or 16450 Universal Asynchronous Receiver Transmitter (UART) as their key
component. Although these UARTs can operate at high speeds, they do not assist
the PC’s microprocessor in dealing with high-speed data transfer. Under Windows,
in particular, data can be lost at high baud rates using these UARTs. If this data loss
occurs, MERLIN LEGEND Reporter cannot function properly.
Whenever possible, select a serial port card which uses the 16550 UART. This
industry standard UART is an improved version of the 16450 with hardware support
to help offload the microprocessor during high-speed data transfers. Windows has
built-in support for the 16550, so no special software configuration is required to
obtain the benefits of the 16550’s enhanced capabilities. In addition, any high-speed
peripheral can benefit from the 16550 (for example, a 14.4 Kbps data and/or fax
modem).
