NAME
dmc —
DEC DMC-11/DMR-11 point-to-point
serial communications device
SYNOPSIS
dmc0 at uba0 csr 167600
DESCRIPTION
NOTE: This driver has not been ported from
4.4BSD yet.
The
dmc interface provides access to a point-to-point
communications device 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 Maintenance mode (generally useless) |
2 |
DDCMP Half Duplex, primary station |
3 |
DDCMP Half Duplex, secondary station |
The host's address must be specified with an
SIOCSIFADDR
ioctl(2), and the destination
address specified with a
SIOCSIFDSTADDR
ioctl(2), before the interface
will transmit or receive any packets.
ROUTING
The driver places a HOST entry in the kernel routing tables for the address
given in the
SIOCSIFDSTADDR
ioctl(2). To use the DMC as a
link between 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 routine.
- dmc%d: unknown address type
%d.
- An input packet was received which contained 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),
vax/vax/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 earlier
drivers, including the
4.2BSD version.