COM(4)                    OpenBSD Programmer's Manual                   COM(4)

NAME
     com, pccom - serial communications interface

SYNOPSIS
     com0 at isa? port "IO_COM1" irq 4
     com1 at isa? port "IO_COM2" irq 3

     pccom0 at isa? port "IO_COM1" irq 4
     pccom1 at isa? port "IO_COM2" irq 3
     pccom* at isapnp?

DESCRIPTION
     The com and pccom drivers provide support for NS8250-, NS16450-,
     NS16550-, ST16650-, and TI16750-based EIA RS-232C (CCITT V.28) communica-
     tions interfaces.  The pccom driver also supports the XR16850 UART.

     The NS8250 and NS16450 have single character buffers, the NS16550 has a
     16 character buffer, while the ST16650 has a 32 character buffer, and the
     TI16750 has a 64 character buffer.  The XR16850 has a 128 character
     buffer.

     The com and pccom drivers are mutually exclusive; both may not be present
     in the same system at the same time.  Attempting to compile such a system
     will fail.

     Input and output for each line may set to one of following baud rates;
     50, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200,
     38400, 57600, or 115200, or any other baud rate which is a factor of
     115200.

FILES
     /dev/tty00
     /dev/tty01
     /dev/cua00
     /dev/cua01

DIAGNOSTICS
     com%d: %d silo overflows  The input ``silo'' has overflowed and incoming
     data has been lost.

     com%d: weird interrupt: iir=%x  The device has generated an unexpected
     interrupt with the code listed.

SEE ALSO
     ast(4), rtfps(4), tty(4)

HISTORY
     The com driver was originally derived from the HP9000/300 dca driver and
     is currently under development.

BUGS
     Data loss is possible on busy systems with unbuffered UARTs at high
     speed.

     The name of this driver and the constants which define the locations of
     the various serial ports are holdovers from DOS.

OpenBSD 3.0                      July 12, 1998                               1
