DMC(4)

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

SYNOPSIS
/sys/conf/SYSTEM:
	NDMC	dmc_controllers	# DMC11

DESCRIPTION
The dmc interface provides access to a point-to-point communications device which runs at either 1 Mb/s or 56 Kb/s. DMC-11's 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-11's are a more recent design and thus are preferred over DMC-11's. The NXMT and NRCV constants in the driver should 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", for more information see the adb script /usr/share/adb/dmcstats, or the DMC11 technical manual.

The host's address must be specified with an SIOCSIFADDR ioctl, 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 address given in the SIOCSIFDSTADDR ioctl. 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
intro(4N), inet(4F)

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.