cxb(4)cxb(4)Namecxb - CXB16 communications interface
device dhu0 at uba0 csr 0160440 flags 0xffff vector dhurint dhuxint
A CXB16 provides 16 data leads-only communication lines with no modem
control. The CXB16 conforms to RS422A. The device behaves and looks
just like a DHV11 (with the exception of modem control and number of
lines) and is specified in the configuration line the same as a DHV11
device. Each line attached to the CXB16 communications interface
behaves as described in and can be set to run at any of 16 speeds. See
for the encoding.
A flags field of 0xffff must be used to specify that all lines are to
operate as hardwired. This is done to prevent the line from being
treated as a modem control line.
The dhu driver normally interrupts on each input character. The and
devices operate under the control of the dhu 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 then prints 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.
FilesSee Alsotty(4), MAKEDEV(8)