DHU(4)                 OpenBSD Programmer's Manual (VAX)                DHU(4)

NAME
     dhu - DHU-11/DHV-11 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 utilize ioctl such as ifconfig(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]

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 NetBSD 1.1A.

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

OpenBSD 2.9                     March 27, 1991                               1
