COM(4)                OpenBSD Programmer's Manual (Arm32)               COM(4)

NAME
     com - serial communications interface

SYNOPSIS
     com0 at mainbus? base 0x00210fe0
     com1 at mainbus? base 0x00210be0

DESCRIPTION
     The com driver provides support for NS8250-, NS16450-, and NS16550-based
     EIA RS-232C (CCITT V.28) communications interfaces.  The NS8250 and
     NS16450 have single character buffers, and the NS16550 has a 16 character
     buffer.

     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.

     If ``flags 1'' is specified, the com driver will not set the MCR_IENABLE
     bit on the UART.  This is mainly for use on AST multiport boards, where
     the MCR_IENABLE bit is used to control whether or not the devices use a
     shared interrupt.

FILES
     /dev/tty00

     /dev/tty01

     /dev/tty02

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
     tty(4)

HISTORY
     The com driver was originally derived from the i386 com 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 2.6                      July 28, 1995                               1
