NAME    [Toc]    [Back]

     dhu - DHU-11/DHV-11 communications multiplexer

SYNOPSIS    [Toc]    [Back]

     dhu0 at uba0 csr 0160440

DESCRIPTION    [Toc]    [Back]

     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(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    [Toc]    [Back]

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

NOTES    [Toc]    [Back]

     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    [Toc]    [Back]

     tty(4), uba(4)

HISTORY    [Toc]    [Back]

     The  dhu driver appeared in 4.3BSD.  A new dhu driver showed
up in NetBSD
     1.1A.

BUGS    [Toc]    [Back]

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

OpenBSD      3.6                          March      27,     1991