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dhq(4) [ultrix man page]

dhq(4)							     Kernel Interfaces Manual							    dhq(4)

       dhq - DHQ11 communications interface

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

       A DHQ11 provides eight communication lines with modem control.

       Each  line attached to the DHQ11 communications multiplexer behaves as described in Input and output for each line can be set independently
       to run at any of 16 speeds.  See for the coding.

       Bit i of flags can be specified for a DHQ11 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 would cause the third line to be treated in this way.
       The driver operates under the control of the driver.

       dhu%d %d: DMA ERROR
       The indicated channel failed to transfer DMA data within 21.3 microseconds of the bus request being acknowledged or there was a memory par-
       ity error.

       dhu%d: DIAG. FAILURE
       The DHQ11 failed the diagnostics that run at initialization time.

       dhu%d: recv. 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.	Interrupts are disabled, and the system then prints a message on the console.

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


See Also
       tty(4), MAKEDEV(8)


Check Out this Related Man Page

DHU(4)							     Kernel Interfaces Manual							    DHU(4)

dhu - DHU-11 communications multiplexer SYNOPSIS
/sys/conf/SYSTEM: NDHU dhu_units # DHU11 /etc/dtab: #Name Unit# Addr Vector Br Handler(s) # Comments du ? 160020 310 5 dhurint dhuxint # dhu11 terminal mux major device number(s): raw: 4 minor device encoding: bits 0017 specify line on DHU unit bits 0060 specify DHU unit bit 0100 specify RTS/CTS flow control bit 0200 specifies non-blocking open (``CD always on'') 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 indepen- dently be set to run at any of 13 speeds (50, 200 and 38400 baud are not available); see tty(4) for the encoding. Bit 0200 of the minor device number for DHU lines may be set to say that a line is not properly connected, and that the line should be treated as hard-wired with carrier always present. Thus creating the special character device node "4, 130" via mknod /dev/ttyS2 c 4 130 would cause line ttyS2 to be treated in this way. Turning on bit 6 (adding 64) to the minor device number via mknod /dev/ttyS2 c 4 194 enables RTS/CTS flow control. 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
dhu(%d,%d) NXM. No response from UNIBUS on a DMA transfer within a timeout period. This has never been observed on a PDP-11 and is believed to be a carryover from the VAX driver when it was ported. It is not serious. dhu%d %d overruns. The character input silo overflowed before it could be serviced. This message is printed only at line close time rather than on each overrun error. Kernel printf's are not interrupt driven and caused more overruns by blocking interrupts for lengthy periods of time. 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. The 4 40-way cables are a pain. 3rd Berkeley Distribution May 31, 1997 DHU(4)
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