DHU(4) BSD/vax Kernel Interfaces Manual DHU(4)NAMEdhu — DHU-11 communications multiplexer
SYNOPSIS
device dhu0 at uba0 csr 0160440 vector dhurint dhuxint
DESCRIPTION
A DHU-11 provides 16 communication lines.
An optional argument flags may be supplied with the device specification
in the config file indicating that the line corresponding to bit number i
is not properly connected, and should be treated as hard-wired with car‐
rier always present. Thus specifying ‘flags 0x0004’ for dhu0 would cause
line ttyS2 to be treated in this way.
Normal I/O control parameters for individual lines are managed by
ioctl(2) calls. Individual DHU-11 lines may be configured to run at any
of 13 speeds (50, 200 and 38400 baud are not available); the speed may be
set via getty(8) or stty(1) or may be communicated by other programs
which utilize ioctl such as ifcongif(8), see tty(4).
The DHU-11 driver normally uses input silos and delays receiver inter‐
rupts by 20 milliseconds rather than taking an interrupt on each input
character.
FILES
/dev/tty[S-Z][0-9a-f]
DIAGNOSTICS
dhu(%d,%d): NXM fault. No response from UNIBUS on a DMA transfer within
a timeout period. This is often followed by a UNIBUS adapter error.
This occurs most frequently when the UNIBUS is heavily loaded and when
devices which hog the bus (such as RK07s) are present. It is not seri‐
ous.
dhu%d: silo overflow. The 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 may then print a message
on the console with interrupts disabled.
NOTES
The driver currently does not make full use of the hardware capabilities
of the DHU-11, for dealing with XON/XOFF flow-control or hard-wired lines
for example.
Although the devices are not the same, a DHU-11 can convince the DH-11
autoconfiguration code that it is a DH-11.
The 4 40-way cables are a pain.
SEE ALSOtty(4)HISTORY
The dhu driver appeared in 4.3BSD.
4.3 Berkeley Distribution June 5, 1993 4.3 Berkeley Distribution