4.3BSD - /usr/man/cat4/dhu.0

DHU(4)                                                                  DHU(4)


NAME
       dhu - DHU-11 communications multiplexer

SYNOPSIS
       device dhu0 at uba0 csr 0160440 vector dhurint dhuxint

DESCRIPTION
       A DHU-11 provides 16 communication lines.

       Each  line attached to the DHU-11 communications multiplexer behaves as
       described in tty(4).  Input and output for each line may  independently
       be  set  to  run  at  any  of 13 speeds (50, 200 and 38400 baud are not
       available); see tty(4) for the encoding.

       Bit i of flags may be specified for a DHU-11 to say that a line is  not
       properly  connected,  and that the line should be treated as hard-wired
       with carrier always present.  Thus specifying ‘‘flags 0x0004’’  in  the
       specification of dhu0 would cause line ttyS2 to be treated in this way.

       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]

SEE ALSO
       tty(4)

DIAGNOSTICS
       dhu(%d,%d): NXM fault.  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.

       dhu%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 may then print a  mes‐
       sage on the console with interrupts disabled.

NOTES
       The  driver  currently does not make full use of the hardware capabili‐
       ties 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.


4.3 Berkeley Distribution       April 27, 1986                          DHU(4)