dhu.4

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)dhu.4	2.6	8/19/87
.TH dhu 4 VAX
.SH Name
dhu \- DHU11 communications interface
.SH Syntax
.B "device dhu0 at uba? csr 0160440 flags 0x???? vector dhurint dhuxint"
.SH Description
.NXS "dhu interface" "DHU11 communications interface"
.NXR "DHU11 communications interface" 
A DHU11 provides 16 communication lines with modem control.
.PP
Each line attached to the DHU11 communications multiplexer
behaves as described in
.MS tty 4 .
Input and output for each line can be set independently
to run at any of 16 speeds.
See
.MS tty 4
for the coding.
.PP
Bit
.I i
of flags can be specified for a DHU11
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 
.PN dhu0
would cause the third line tty02 to be treated in this way.
.SH Diagnostics
.B "dhu%d %d: DMA ERROR"
.br 
The indicated channel failed to transfer DMA
data within 21.3 microseconds of the bus request being acknowledged or
there was a memory parity error.
This is often followed by a UNIBUS adapter
error, which occurs most frequently when the UNIBUS is heavily loaded
and when devices such as rk07s, which monopolize the bus, are present.
.PP
.B "dhu%d: DHU HARDWARE ERROR.  TX.DMA.START failed"
.br 
The 
.PN dhu 
failed to clear the start bit.  Normally, this is cleared to signal 
that a DMA transfer has completed.
.PP
.B "dhu%d: DIAG. FAILURE"
.br 
The DHU11 failed the diagnostics that
run at initialization time.
.PP
.B "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 elevated priority.  Interrupts are
disabled, and the system then prints a message on the console.
.SH Files
.TP 15
.PN /dev/tty??

.TP
.PN /dev/ttyd?
(modem lines only)
.SH See Also
tty(4), MAKEDEV(8)