dhq(4)dhq(4)Namedhq - 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 microsec‐
onds of the bus request being acknowledged or there was a memory parity
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 elevated
priority. Interrupts are disabled, and the system then prints a mes‐
sage 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 Alsotty(4), MAKEDEV(8)dhq(4)