dhv(4)
NAME
dhv − DHV-11 communications multiplexer
dhu
SYNTAX
device dhv0 at uba0 csr 0160440 flags 0xff vector dhurint dhuxint
DESCRIPTION
A dhv-11 provides 8 communication lines with partial modem control, adequate for UNIX dialup use. Each line attached to the DHV-11 communications multiplexer behaves as described in tty(4) and may be set to run at any of 16 speeds; see tty(4) 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 hard-wired with carrier always present. Thus specifying “flags 0x04” in the specification of dhv0 would cause line tty02 to be treated in this way.
The dhv driver normally interrupts on each input character.
NOTE
The dhv and dhu drivers have been combined.
DIAGNOSTICS
dhv%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.
dhv%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.
dhv%d: DIAG. FAILURE. This indicates that the dhv internal diagnostics have detected an error.
FILES
/dev/tty??
/dev/ttyd?dialups