4.3BSD-UWisc/man/cat4/dhu.4

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DHU(4)              UNIX Programmer's Manual               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 _t_t_y(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 _t_t_y(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 interrupts 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 message on the console with
     interrupts disabled.

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.




Printed 12/27/86         April 27, 1986                         1






DHU(4)              UNIX Programmer's Manual               DHU(4)



     The 4 40-way cables are a pain.






















































Printed 12/27/86         April 27, 1986                         2