dhv(4)dhv(4)Namedhv - DHV11 communications interface
device dhu0 at uba0 csr 0160440 flags 0x?? vector dhurint dhuxint
A DHV11 provides eight communication lines with partial modem control,
adequate for UNIX dialup use. Each line attached to the DHV11 communi‐
cations 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.
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 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.
See Alsotty(4), MAKEDEV(8)dhv(4)