dhv(4) Kernel Interfaces Manual 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 com-
munications interface behaves as described in and can be set to run at any of 16 speeds. See 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 driver normally interrupts on each input character. The and devices operate under the control of the 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 ele-
vated priority, as the system will then print 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 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 internal diagnostics have detected an error.
dhu%d: DHU HARDWARE ERROR. TX.DMA.START failed
The failed to clear the start bit. Normally, this is cleared to signal that a DMA transfer has completed.
Files
Dialups
See Also
tty(4), MAKEDEV(8)
dhv(4)
