.\"	$OpenBSD: rtfps.4,v 1.6 2002/09/26 07:55:40 miod Exp $
.\"
.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the Systems Programming Group of the University of Utah Computer
.\" Science Department.
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.\"	This product includes software developed by the University of
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.\"     from: @(#)dca.4	5.2 (Berkeley) 3/27/91
.\"	from: Id: com.4,v 1.1 1993/08/06 11:19:07 cgd Exp
.\"
.Dd August 7, 1994
.Dt RTFPS 4
.Os
.Sh NAME
.Nm rtfps
.Nd multiplexing serial communications interface
.Sh SYNOPSIS
.Cd "rtfps0 at isa? port 0x1230 irq 10"
.Cd "com* at rtfps? slave ?"
or
.Cd "pccom* at rtfps? slave ?"
.Sh DESCRIPTION
The
.Nm
driver provides support for IBM RT PC boards that multiplex together up to four
.Rn EIA
.Tn RS-232C
.Pf ( Tn CCITT
.Tn V.28 )
or
.Tn RS-422A
communications interfaces.
.Pp
Each
.Nm
device is the master device for up to four
.Nm com
devices.
The kernel configuration specifies these
.Nm com
devices as slave devices of the
.Nm
device, as shown in the synopsis.
The
.Tn port
specification for the
.Nm
device is used to compute the base addresses for the
.Nm com
subdevices.
.Sh FILES
.Bl -tag -width Pa
.It Pa /dev/tty0?
.El
.Sh SEE ALSO
.Xr com 4 ,
.Xr intro 4 ,
.Xr isa 4
.Sh HISTORY
The
.Nm
driver was written by Charles Hannum, based on the
.Nm ast
driver.
.Sh BUGS
The
.Nm
driver is unlikely to work on non-EISA and non-PCI machines.
The ISA bus only asserts 10 I/O address lines, and this is not enough.
.Pp
Even on EISA and PCI machines, some address conflicts have been observed.
On one machine, the second port always conflicted with something (though
it's not clear what) and caused strange results.
Disabling the second port in the kernel config allowed the other three
ports to function correctly.