NetBSD/share/man/man4/ast.4

.\"	$NetBSD: ast.4,v 1.12 2004/05/11 22:42:47 wiz Exp $
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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 March 30, 1994
.Dt AST 4
.Os
.Sh NAME
.Nm ast
.Nd
multiplexing serial communications interface
.Sh SYNOPSIS
.Cd "ast0 at isa? port 0x1a0 irq 5"
.Cd "com2 at ast? slave ?"
.Cd "com3 at ast? slave ?"
.Cd "com4 at ast? slave ?"
.Cd "com5 at ast? slave ?"
.Sh DESCRIPTION
The
.Nm ast
driver provides support for boards that multiplex together up to four
.Tn EIA
.Tn RS-232C
.Pf ( Tn CCITT
.Tn V.28 )
communications interfaces.
Apparently the original maker of hardware
using this multiplexing protocol was AST.
.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 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 and the port for the interrupt multiplexing register.
.Sh FILES
.Bl -tag -width Pa
.It Pa /dev/tty0?
.El
.Sh SEE ALSO
.Xr com 4
.Sh HISTORY
The
.Nm
driver was written by Roland McGrath and placed into the public
domain.