dhu(4) — VAX
Name
dhu − DHU11 communications interface
Syntax
device dhu0 at uba? csr 0160440 flags 0x???? vector dhurint dhuxint
Description
A DHU11 provides 16 communication lines with modem control.
Each line attached to the DHU11 communications multiplexer behaves as described in tty(.). Input and output for each line can be set independently to run at any of 16 speeds. See tty() for the coding.
Bit i of flags can be specified for a DHU11 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 0x0004” in the specification of dhu0 would cause the third line tty02 to be treated in this way.
Diagnostics
dhu%d %d: DMA ERROR
The indicated channel failed to transfer DMA data within 21.3 microseconds of the bus request being acknowledged or there was a memory parity error. This is often followed by a UNIBUS adapter error, which occurs most frequently when the UNIBUS is heavily loaded and when devices such as rk07s, which monopolize the bus, are present.
dhu%d: DHU HARDWARE ERROR. TX.DMA.START failed
The dhu failed to clear the start bit. Normally, this is cleared to signal that a DMA transfer has completed.
dhu%d: DIAG. FAILURE
The DHU11 failed the diagnostics that run at initialization time.
dhu%d: recv. 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. Interrupts are disabled, and the system then prints a message on the console.
Files
/dev/tty??
/dev/ttyd? (modem lines only)