dhu(4)dhu(4)Namedhu - DHU11 communications interface
device dhu0 at uba? csr 0160440 flags 0x???? vector dhurint dhuxint
A DHU11 provides 16 communication lines with modem control.
Each line attached to the DHU11 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 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 would cause the third line tty02 to be treated in this
dhu%d %d: DMA ERROR
The indicated channel failed to transfer DMA data within 21.3 microsec‐
onds 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.
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.
dhu%d: DIAG. FAILURE
The DHU11 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 elevated priority. Interrupts are disabled, and
the system then prints a message on the console.
(modem lines only)
See Alsotty(4), MAKEDEV(8)