NAME
dh —
DH-11/DM-11 serial multiplexer
device interface
SYNOPSIS
dh0 at uba0 csr 0160020 vector dhrint dhxint
[
flags]
dm0 at uba0 csr 0170500 vector dmintr
[
flags]
DESCRIPTION
NOTE: This driver has not been ported from
4.4BSD yet.
A DH-11 provides 16 serial communication lines; DM-11s may optionally be paired
with DH-11s to provide modem control for the lines.
An optional argument
flags may be supplied with the device
specification in the
config(1) file indicating
that the line corresponding to bit number
i is not
properly connected, and should be treated as hard-wired with carrier always
present. Thus specifying ‘
flags 0x0004
’
for
dh0
would cause line
ttyh2 to be
treated in this way.
Normal I/O control parameters for individual lines are managed by
ioctl(2) calls. Line speeds
may be initiated via
getty(8)
and
stty(1) or may be
communicated by other programs which use
ioctl(2) such as
ifconfig(8), see
tty(4).
The
dh 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[h-o][0-9a-f]
-
- /dev/ttyd[0-9a-f]
-
DIAGNOSTICS
- dh%d: NXM.
- 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 serious.
- dh%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 will then print a message on the
console with interrupts disabled. It is not serious.
SEE ALSO
tty(4)
HISTORY
A
dh driver appeared in
Version 6
AT&T UNIX.