.\" Copyright (c) 1980 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)dz.4	6.2 (Berkeley) 1/28/88
.\"
.TH DZ 4 "January 28, 1988"
.UC 2
.SH NAME
dz \- DZ-11 communications multiplexer
.SH SYNOPSIS
.ft B
.nf
/sys/conf/SYSTEM:
	NDZ	\fIdz_units\fP	# DZ11; NDZ is in units of boards (8 each)

/etc/dtab:
.ta .5i +\w'#Name 'u +\w'Unit# 'u +\w'177777 'u +\w'Vector 'u +\w'Br 'u +\w'xxxxxxx 'u +\w'xxxxxxx 'u
	#Name	Unit#	Addr	Vector	Br	Handler(s)		# Comments
	dz	?	160100	310	5	dzrint	dzdma	# dz11 terminal mux
.DT

major device number:
	raw: 2
minor device encoding:
	bits 0007 specify line on DZ unit
	bits 0170 specify DZ unit
	bit  0200 specifies non-blocking open (``CD always on'')
.SH DESCRIPTION
A DZ11 provides 8 communication lines with partial modem control,
adequate for UNIX dialup use.
Each line attached to the DZ11 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 0200
of the minor device number for DZ lines
may be set to say that a line is not properly
connected, and that the line should be treated as hard-wired with carrier
always present.  Thus creating the special character device node "2, 130" via
.I "mknod /dev/tty02 c 2 130"
would cause line tty02 to be treated in this way.
.PP
The
.I dz
driver monitors the rate of input on each board,
and switches between the use of character-at-a-time interrupts
and input silos.
While the silo is enabled during periods of high-speed input,
the driver polls for input 30 times per second.
.SH FILES
.ta \w'/dev/MAKEDEV.local  'u
/dev/tty[0-9][0-9]
.br
/dev/ttyd[0-9a-f]		dialups
.br
/dev/MAKEDEV	script to create special files
.br
/dev/MAKEDEV.local	script to localize special files
.DT
.SH "SEE ALSO"
tty(4),
dtab(5),
autoconfig(8)
.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.
It is not serious.