cxa(4) Kernel Interfaces Manual cxa(4)
Name
cxa - CXA16 communications interface
Syntax
device dhu0 at uba0 csr 0160440 flags 0xffff vector dhurint dhuxint
Description
A CXA16 provides 16 data-leads-only communication lines with no modem control. The CXA16 conforms to RS423A. 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 CXA16 communications multiplexer 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 driver.
Diagnostics
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 ele-
vated 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.
Files
See Also
tty(4), MAKEDEV(8)
cxa(4)
