DMC(4)                 OpenBSD Programmer's Manual (VAX)                DMC(4)

NAME
     dmc - DEC DMC-11/ DMR-11 point-to-point communications device

SYNOPSIS
     device dmc0 at uba0 csr 167600 vector dmcrint dmcxint

DESCRIPTION
     The dmc interface provides access to a point-to-point communications de-
     vice which runs at either 1 Mb/s or 56 Kb/s.  DMC-11s communicate using
     the DEC DDCMP link layer protocol.

     The dmc interface driver also supports a DEC DMR-11 providing point-to-
     point communication running at data rates from 2.4 Kb/s to 1 Mb/s.
     DMR-11s are a more recent design and thus are preferred over DMC-11s. The
     NXMT and NRCV constants in the driver may be increased in this case, as
     the DMR can accept up to 64 transmit and receive buffers, as opposed to 7
     for the DMC.

     The configuration flags specify how to set up the device,

           0      full duplex DDCMP (normal mode)
           1      DDCMP Maintence mode (generally useless)
           2      DDCMP Half Duplex, primary station
           3      DDCMP Half Duplex, secondary station

     Several device error counters are available via adb(1), for more informa-
     tion see the adb script /usr/lib/adb/dmcstats, or the DMC-11 technical
     manual.

     The host's address must be specified with an SIOCSIFADDR ioctl(2), and
     the destination address specified with a SIOCSIFDSTADDR ioctl, before the
     interface will transmit or receive any packets.

ROUTING
     The driver places a HOST entry in the kernel routing tables for the ad-
     dress given in the SIOCSIFDSTADDR ioctl.  To use the DMC as a link be-
     tween local nets, the route to the remote net must be added manually with
     the route(8) command, or by the use of the routing process routed(8) on
     each end of the link.

DIAGNOSTICS
     dmc%d: bad control %o.  A bad parameter was passed to the dmcload rou-
     tine.

     dmc%d: unknown address type %d.  An input packet was received which con-
     tained a type of address unknown to the driver.

     DMC fatal error 0%o.  A fatal error in DDMCP occurred, causing the device
     to be restarted.

     DMC soft error 0%o.  A non-fatal error in DDMCP has occurred.

     dmc%d: af%d not supported.  The interface was handed a message which has
     addresses formatted in an unsuitable address family.

SEE ALSO
     inet(4), intro(4)

HISTORY
     The dmc driver appeared in 4.2BSD.

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 earli-
     er drivers, including the 4.2BSD version.

OpenBSD 2.9                     March 27, 1991                               2
