COM(4)                  NetBSD Kernel Interfaces Manual                 COM(4)

NAME
     com -- serial communications interface

SYNOPSIS
     com0 at isa? port "IO_COM1" irq 4
     com1 at isa? port "IO_COM2" irq 3
     com* at acpi?
     com* at cardbus?
     com* at isapnp?
     com* at mca? slot ?
     com* at mhzc?
     com* at ofisa?
     com* at pcmcia?
     com* at pcmcom?
     com* at pnpbios? index ?
     com* at puc? port ?
     com* at xirc?
     options COM_HAYESP
     options RND_COM

   Arm32
     com0 at mainbus? base 0x00210fe0
     com1 at mainbus? base 0x00210be0

   HP 9000/300 and 400 Series
     com* at dio? scode ?
     com* at frodo? offset ?

   IBM PowerPC 4xx
     com* at opb?

   SPARC
     com* at ebus?
     com* at obio0

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.

     The ttyXX devices are traditional dial-in devices; the dtyXX devices are
     used for dial-out.  (See tty(4).)

     The COM_HAYESP kernel option adds support for the Hayes ESP serial board.

     With options RND_COM enabled, the com driver can be used to collect
     entropy for the rnd(4) entropy pool.  The entropy is generated from
     interrupt randomness.

   Arm32 specific
     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/dty00
     /dev/dty01
     /dev/dty02
     /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
     acpi(4), ast(4), cardbus(4), isa(4), isapnp(4), mca(4), mhzc(4),
     ofisa(4), pcmcia(4), pcmcom(4), pnpbios(4), puc(4), rtfps(4), tty(4),
     xirc(4)

HISTORY
     The com driver was originally derived from the HP9000/300 dca driver.

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.

NetBSD 5.0_STABLE                June 1, 2007                NetBSD 5.0_STABLE
