cxy(4)
Name
cxy − CXY08 communications interface
Syntax
device dhu0 at uba0 csr 0160440 flags 0x?? vector dhurint dhuxint
Description
A CXY08 provides eight communication lines with modem control adequate for UNIX dialup use. The device behaves and looks just like a DHV11 and is specified in the configuration line the same as a DHV11 device. Each line attached to the CXY08 communications interface behaves as described in tty() and can be set to run at any of 16 speeds. See tty() for the encoding.
Bit i of flags can be specified for a cxy device 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 dhu0 would cause line tty02 to be treated in this way.
The dhu driver normally interrupts on each input character.
Note
The cxa, cxb, cxy, dhv, and dhq devices operate under the control of the dhu 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 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 cxy 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 cxy internal diagnostics have detected an error.
dhu%d: DHU HARDWARE ERROR. TX.DMA.START failed
The cxy failed to clear the start bit. Normally, this is cleared to signal that a DMA transfer has completed.
Files
/dev/tty??
/dev/ttyd? Dialups