DHU(4)

NAME
dhu - DHU-11/DHV-11 serial communications multiplexer

SYNOPSIS
dhu0 at uba0 csr 0160440

DESCRIPTION
A DHU-11 provides 16 communication lines.

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 use ioctl(2) such as ifconfig(8), see tty(4).

The DHU-11 driver normally uses input silos and delays receiver interrupts by 20 milliseconds rather than taking an interrupt on each input character.

FILES
/dev/tty[S-Z][0-9a-f]

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 ALSO
tty(4)

HISTORY
The dhu driver appeared in 4.3BSD.
A new dhu driver showed up in 1.2BSD.

BUGS
Even if the dhu hardware supports DMA, the driver cannot make use of this capability.