dhv(4)							     Kernel Interfaces Manual							    dhv(4)

Name
       dhv - DHV11 communications interface

Syntax
       device dhu0 at uba0 csr 0160440 flags 0x?? vector dhurint dhuxint

Description
       A  DHV11 provides eight communication lines with partial modem control, adequate for UNIX dialup use.  Each line attached to the DHV11 com-
       munications interface behaves as described in and can be set to run at any of 16 speeds.  See for the encoding.

       Bit i of flags may be specified for a DHV to say that a line is not properly connected and that the line should be  treated  as	hardwired,
       with  carrier  always  present.	 Thus, specifying ``flags 0x04'' in the specification of dhu0 would cause line tty02 to be treated in this
       way.

       The driver normally interrupts on each input character.	The and devices operate under the control of the driver.

Diagnostics
       dhu%d: receive fifo overflow
       The character input fifo overflowed before it could be serviced.  This can happen if a hard error occurs when the CPU is running with  ele-
       vated  priority, as the system will then print a message on the console with interrupts disabled.  This can cause a few input characters to
       be lost to users.  It is not serious.

       dhu%d:%d DMA ERROR
       A DMA transfer error has occurred.  The unit number and line number are printed.  This means that  the  channel	indicated  has	failed	to
       transfer  DMA data within 10.7 microseconds of the bus request being acknowledged or that there is a memory parity error.  This may cause a
       few output characters to be lost.

       dhu%d: DIAG. FAILURE
       This indicates that the internal diagnostics have detected an error.

       dhu%d: DHU HARDWARE ERROR.  TX.DMA.START failed
       The failed to clear the start bit.  Normally, this is cleared to signal that a DMA transfer has completed.

Files
       Dialups

See Also
       tty(4), MAKEDEV(8)

																	    dhv(4)