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.
/dev/tty[h-o][0-9a-f]
/dev/ttyd[0-9a-f]
AT&T UNIX
.