.\"	$OpenBSD: dmc.4,v 1.5 2001/06/23 07:04:23 pjanzen Exp $
.\"	$NetBSD: dmc.4,v 1.3 1996/03/03 17:13:22 thorpej Exp $
.\"
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.\"     from: @(#)dmc.4	6.5 (Berkeley) 3/27/91
.\"
.Dd March 27, 1991
.Dt DMC 4 vax
.Os
.Sh NAME
.Nm dmc
.Nd
.Tn DEC
.Tn DMC-11 Ns / Tn DMR-11
point-to-point communications device
.Sh SYNOPSIS
.Cd "device dmc0 at uba0 csr 167600 vector dmcrint dmcxint"
.Sh DESCRIPTION
The
.Nm dmc
interface provides access to a point-to-point communications
device which runs at either 1 Mb/s or 56 Kb/s.
.Tn DMC-11 Ns s
communicate
using the
.Tn DEC DDCMP
link layer protocol.
.Pp
The
.Nm dmc
interface driver also supports a
.Tn DEC
.Tn DMR-11
providing point-to-point
communication running at data rates from 2.4 Kb/s to 1 Mb/s.
.Tn DMR-11 Ns s
are a more recent design and thus are preferred over
.Tn DMC-11 Ns s .
The
.Dv NXMT
and
.Dv NRCV
constants in the driver may be increased in this case,
as the
.Tn DMR
can accept up to 64 transmit and receive buffers, as opposed
to 7 for the
.Tn DMC .
.Pp
The configuration flags specify how to set up the device,
.Bl -column xxx -offset indent
0	full duplex DDCMP (normal mode)
1	DDCMP Maintenance mode (generally useless)
2	DDCMP Half Duplex, primary station
3	DDCMP Half Duplex, secondary station
.El
.Pp
Several device error counters are available via
.Xr adb 1 ,
for
more information see the
.Xr adb
script
.Pa /usr/lib/adb/dmcstats ,
or the
.Tn DMC-11
technical manual.
.Pp
The host's address must be specified with an
.Dv SIOCSIFADDR
.Xr ioctl 2 ,
and the destination address specified with a
.Dv SIOCSIFDSTADDR
.Xr ioctl ,
before the interface will transmit or receive any packets.
.Sh ROUTING
The driver places a
.Tn HOST
entry in the kernel routing tables for the
address given in the
.Dv SIOCSIFDSTADDR
.Xr ioctl.
To use the
.Tn DMC
as a
link between local nets, the route to the remote net must be added manually
with the
.Xr route 8
command, or by the use of the routing process
.Xr routed 8
on each end of the link.
.Sh DIAGNOSTICS
.Bl -diag
.It dmc%d: bad control %o.
A bad parameter was passed to the
.Em dmcload
routine.
.Pp
.It dmc%d: unknown address type %d.
An input packet was received which contained a type of
address unknown to the driver.
.Pp
.It DMC fatal error 0%o.
A fatal error in
.Tn DDMCP
occurred, causing the device to be restarted.
.Pp
.It DMC soft error 0%o.
A non-fatal error in
.Tn DDMCP
has occurred.
.Pp
.It dmc%d: af%d not supported.
The interface was handed a message which has
addresses formatted in an unsuitable address family.
.El
.Sh SEE ALSO
.Xr inet 4 ,
.Xr intro 4
.Sh HISTORY
The
.Nm
driver appeared in
.Bx 4.2 .
.Sh BUGS
The current version of the driver uses a link-level encapsulation
so that multiple protocol types may be used.
It is thus incompatible with earlier drivers,
including the
.Bx 4.2
version.