.TH cxa 4.SH Namecxa \- CXA16 communications interface.SH Syntax.B "device dhu0 at uba0 csr 0160440 flags 0xffff vector dhurint dhuxint".SH Description.NXR "CXA16 communications interface"A CXA16 provides 16 data-leads-only communication lines with no modem control..NXR "RS423A standard"The CXA16 conforms to RS423A.The device behaves and looks justlike a DHV11(with the exception of modem control and number of lines)and is specified in the configuration line the sameas a DHV11 device.Each line attached to the CXA16 communications multiplexerbehaves as described in.MS tty 4and can be set to run at any of 16 speeds; see.MS tty 4for the encoding..PPA flags field of 0xffff must be used to specify that all lines are to operateas hardwired.  This is done to prevent the line from being treated as amodem control line..PPThe dhu driver normally interrupts on each input character..NTThe .PN cxa ,.PN cxb ,.PN cxy ,.PN dhv , and.PN dhqdevices operate under the control of the .PN dhudriver..SH Diagnostics.B "dhu%d: receive fifo overflow".brThe character input fifo overflowedbefore it could be serviced.  This can happen if a hard error occurswhen 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..PP.B "dhu%d:%d DMA ERROR.brA DMA transfer error has occurred.The.PN cxaunit number and line number are printed.This means that the channel indicated has failed to transfer DMA datawithin 10.7 microseconds of the bus request being acknowledged or thatthere is a memory parity error.This may cause a few output characters to be lost..PP.B "dhu%d: DIAG. FAILURE".brThis indicates that the.PN cxainternal diagnostics have detected an error..PP.B "dhu%d: DHU HARDWARE ERROR.  TX.DMA.START failed".brThe .PN cxa failed to clear the start bit.  Normally, this is cleared to signal that a DMA transfer has completed..SH Files.PN /dev/tty??.SH See Alsotty(4), MAKEDEV(8)