.\"	$OpenBSD: addcom.4,v 1.8 2008/05/21 19:05:51 kettenis Exp $
.\"
.\" Copyright (c) 2001 Jason L. Wright (jason@thought.net)
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.Dd $Mdocdate: May 21 2008 $
.Dt ADDCOM 4
.Os
.Sh NAME
.Nm addcom
.Nd multiplexing serial communications interface
.Sh SYNOPSIS
.Cd "addcom0 at isa? port 0x108 irq 5"
.Cd "com* at addcom?"
.Sh DESCRIPTION
The
.Nm
driver provides support for Addonics FlexPort 8/S (and probably FlexPort 4/S)
boards that multiplex together up to eight (or four)
.Tn EIA
.Tn RS-232C
.Pf ( Tn CCITT
.Tn V.28 )
communications interfaces.
.Pp
Each
.Nm
device is the master device for up to eight
.Nm com
devices.
The kernel configuration specifies these
.Nm com
devices as slave devices of the
.Nm
device, as shown in
.Sx SYNOPSIS .
The slave ID given for each
.Nm com
device determines which bit in the interrupt multiplexing register is
tested to find interrupts for that device.
The
.Tn port
specification for the
.Nm
device is used to compute the base addresses for the
.Nm com
subdevices.
The port for the interrupt multiplexing register is fixed,
so it is doubtful that more than one
.Nm
can be used in a machine.
.Sh FILES
.Bl -tag -width Pa
.It Pa /dev/tty??
.El
.Sh SEE ALSO
.Xr com 4 ,
.Xr intro 4 ,
.Xr isa 4
.Sh HISTORY
.Ox
support for
.Nm
devices first appeared in
.Ox 3.0 .