dmc.4

<B>Digital的Unix操作系统VAX 4.2源码</B>

.TH dmc 4 VAX
.SH Name
dmc \- DMC11/DMR11 communications interface
.SH Syntax
.B "device dmc0 at uba0 csr 0167600 flags 0x???? vector dmcrint dmcxint"
.SH Description
.NXS "dmc interface" "DMC11 communications interface"
.NXS "dmc interface" "DMR11 communications interface"
.NXR "DMC11 communications interface"
.NXR "DMR11 communications interface"
The
.PN dmc
interface provides access to a point-to-point communications
device that runs at either 1 Mb/s or 56 Kb/s.  DMC11s communicate
using the DDCMP link layer protocol.
.PP
The
.PN dmc
interface driver also supports a DMR11 providing point-to-point
communication running at data rates from 2.4 Kb/s to 1 Mb/s.
DMR11s are a more recent design and are preferred over DMC11s.
.PP
The host address must be specified with an SIOCSIFADDR ioctl
before the interface will transmit or receive any packets.
.PP
Several protocols can be multiplexed over a
.PN dmc
link simultaneously.  Conversely, a
.PN dmc
can be set up such that only one protocol family can use
that device.  If the latter approach is taken, an SIOCSTATE
ioctl must be issued by the protocol family requesting
device ownership.  The family address must appear in the
``if_family'' structure member, and ``if_nomuxhdr'' must
be set.  Before requesting ownership, make sure that access to
the device for all other protocol families is disabled.
.PP
The first byte of the 
.I flags 
word can be set up to indicate
what mode the device should use.  The supported modes are
0 for full duplex, 1 for maintenance mode, and 2 for half
duplex.  In addition, if the device is a
.PN dmr ,
the number of outstanding transmit buffers can be increased
from a default of 7 to a maximum of 24 buffers by specifying
a hexadecimal value in the second byte of the 
.I flags 
word.  For example, if the 
.I flags 
word is set to 0x1800, 24
transmit buffers will be allocated on a device set up to run
full duplex.
.SH Restrictions
Note that maintenance mode should be used only to diagnose 
data link problems.  It is not intended to be used for normal 
data link traffic.
.SH Diagnostics
.B "dmcprobe: can't start device" 
.br
The
.PN dmc
could not be started at boot time.
.PP
.B "dmcinit:  DMC not running"
.br 
The 
.PN dmc
unexpectedly stopped running.
.PP
.B "dmc%d: done unalloc rbuf"
.br 
The
.PN dmc
returned a receive or transmit buffer that was not
allocated to it.
.PP
.B "dmc%d: bad control %o"
.br 
A bad parameter was passed to the
.I dmcload
routine.
.PP
.B "dmc%d: unknown address type %d" 
.br
An input packet was received that contained a type of
address unknown to the driver.
.PP
.B "dmc%d: bad packet address 0x%x" 
.br 
The device returned a buffer with an unexpected buffer
address.
.PP
.B "dmc%d: can't handle af%d"
.br 
The interface was handed a message that has addresses
formatted in an unsuitable address family.  Formerly
reported as
.BR "dmc%d: af%d not supported" .
.PP
.B "dmc%d: internal loopback enable requested"
.br 
The device is being put in internal loopback at a user's
request.
.PP
.B "dmc%d: internal loopback disable requested"
.br 
The device is being taken out of internal loopback at a user's
request.
.PP
.B "DMC FATAL ERROR 0%o"
.br 
.PP
.B "DMC SOFT ERROR 0%o" 
.SH See Also
inet(4f), intro(4n)