dhv(4)
NAME
dhv − DHV11 communications interface
SYNTAX
device dhu0 at uba0 csr 0160440 flags 0x?? vector dhurint dhuxint
DESCRIPTION
A DHV11 provides eight communication lines with partial modem control, adequate for UNIX dialup use. Each line attached to the DHV11 communications interface behaves as described in tty() and may be set to run at any of 16 speeds. See tty() for the encoding.
Bit i of flags may be specified for a DHV 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 dhv 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 will then print a message on the console with interrupts disabled. This may 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 dhv 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 dhv internal diagnostics have detected an error. The dhv failed to clear the start bit. Normally this is cleared to signal that a DMA transfer has completed.
FILES
/dev/tty??
/dev/ttyd?Dialups