3
Windows Driver
special situations, though in in some of those it is even better to just change the configuration of
the other parameters.
8250
The FIFO is totally switched off, as are all other options. The real 8250 UART had a speed
limitation of 57600 bps, this is maintained by software here.
16450
The most common UART in the late 1980 decade. There still is no FIFO available, the
maximum bitrate is raised to 115200 bps. Sometimes this Emulation may be useful, if the
connected device is overrun by the transmitted data. But usually it is better to restrict the
Transmit Buffer length to 1.
16550
The most common UART until today. There are 16 Byte FIFO for transmit and receive
each, and four trigger levels for receive. The built-in serial ports of modern computers use this
UART model, with a maximum speed of 115200 bps, which is 921600 bps on VScom cards.
16650
This UART basically has 32 bytes FIFOfor transmit and receive each, and also four trigger
levels for receive. However this emulation uses 128 Bytes FIFO for receive. Additional
function is automatic Flow Control by RTS/CTS or XON/XOFF.
16750
This is another UART with extended FIFO compared to the 16550 model. In basic con-
figuration ther are 16/16 Byte FIFO, which can be increased to 64/64 Byte. However as
an emulation it uses 128/128 byte FIFO. Also automatic Flow Control by RTS/CTS and
Xon/Xoff is possible.
16850
This is another UART model with 128/128 Byte FIFO.
16950
This is the native mode the ports on the VScom cards are used. In most situations it is
better to use this mode, and restrict the options to a suitable configuration.
February 2010
VScom PCIex Card User Manual
25
