cxb man page on Ultrix

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cxb(4)									cxb(4)

Name
       cxb - CXB16 communications interface

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

Description
       A  CXB16	 provides 16 data leads-only communication lines with no modem
       control.	 The CXB16 conforms to RS422A.	The device behaves  and	 looks
       just  like  a  DHV11 (with the exception of modem control and number of
       lines) and is specified in the configuration line the same as  a	 DHV11
       device.	 Each  line  attached  to  the	CXB16 communications interface
       behaves as described in and can be set to run at any of 16 speeds.  See
       for the encoding.

       A  flags	 field of 0xffff must be used to specify that all lines are to
       operate as hardwired.  This is done to  prevent	the  line  from	 being
       treated as a modem control line.

       The  dhu	 driver	 normally interrupts on each input character.  The and
       devices operate under the control of the dhu 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 elevated
       priority, as the system then prints  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
See Also
       tty(4), MAKEDEV(8)

				      VAX				cxb(4)
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