4.2BSD/usr/man/man4/dz.4

.TH DZ 4 "27 July 1983"
.UC 4
.SH NAME
dz \- DZ-11 communications multiplexer
.SH SYNOPSIS
.B "device dz0 at uba0 csr 0160100 vector dzrint dzxint"
.SH DESCRIPTION
A dz-11 provides 8 communication lines with partial modem control,
adequate for UNIX dialup use.
Each line attached to the DZ-11 communications multiplexer
behaves as described in
.IR tty (4)
and may be set to run at any of 16 speeds; see
.IR tty (4)
for the encoding.
.PP
Bit
.I i
of flags may be specified for a dz to say that a line is not properly
connected, and that the line should be treated as hard-wired with carrier
always present.  Thus specifying ``flags 0x04'' in the specification of dz0
would cause line tty02 to be treated in this way.
.PP
The dz driver normally uses its input silos
and polls for input at each clock tick (10 milliseconds)
rather than taking an interrupt on each input character.
.SH FILES
/dev/tty[0-9][0-9]
.br
/dev/ttyd[0-9a-f]		dialups
.SH "SEE ALSO"
tty(4)
.SH DIAGNOSTICS
.PP
\fBdz%d: silo overflow\fR.  The 64 character input silo overflowed
before it could be serviced.  This can happen if a hard error occurs
when the CPU is running with elevated priority, as the system will
then print a message on the console with interrupts disabled.  If the
Berknet
is running on a
.I dz
line at high speed (e.g. 9600 baud), there is only 1/15th of a second of
buffering capacity in the silo, and overrun is possible.  This may
cause a few input characters to be lost to users and a network
packet is likely to be corrupted, but the network will recover.
It is not serious.