DZ(4)

NAME
dz - DZ-11 communications multiplexer

SYNOPSIS
/sys/conf/SYSTEM:
	NDZ	dz_units	# DZ11; NDZ is in units of boards (8 each)
/etc/dtab:
	#Name	Unit#	Addr	Vector	Br	Handler(s)		# Comments
	dz	?	160100	310	5	dzrint	dzdma	# dz11 terminal mux
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'')

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 tty(4) and may be set to run at any of 16 speeds; see tty(4) for the encoding.

Bit 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 mknod /dev/tty02 c 2 130 would cause line tty02 to be treated in this way.

The 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.

FILES
/dev/tty[0-9][0-9]
/dev/ttyd[0-9a-f]    dialups
/dev/MAKEDEV    script to create special files
/dev/MAKEDEV.local    script to localize special files

SEE ALSO
tty(4), dtab(5), autoconfig(8)

DIAGNOSTICS

dz%d: silo overflow. 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.