DHU

Section: Devices and Network Interfaces (4)
Updated: vax
Index Return to Main Contents

BSD mandoc
BSD 4.3  

NAME

dhu - DHU-11 communications multiplexer  

SYNOPSIS

device dhu0 at uba0 csr 0160440 vector dhurint dhuxint  

DESCRIPTION

A DHU-11 provides 16 communication lines.

An optional argument flags may be supplied with the device specification in the config file indicating that the line corresponding to bit number i is not properly connected, and should be treated as hard-wired with carrier always present. Thus specifying `flags' 0x0004 for dhu0 would cause line ttyS2 to be treated in this way.

Normal I/O control parameters for individual lines are managed by ioctl(2) calls. Individual DHU-11 lines may be configured to run at any of 13 speeds (50, 200 and 38400 baud are not available); the speed may be set via getty(8) or stty(1) or may be communicated by other programs which utilize ioctl such as ifcongif(8), see tty(4).

The DHU-11 driver normally uses input silos and delays receiver interrupts by 20 milliseconds rather than taking an interrupt on each input character.  

FILES

/dev/tty[S-Z][0-9a-f]

 

DIAGNOSTICS

dhu(%d,%d): NXM fault.
No response from UNIBUS on a DMA transfer within a timeout period. This is often followed by a UNIBUS adapter error. This occurs most frequently when the UNIBUS is heavily loaded and when devices which hog the bus (such as RK07 s are present. It is not serious.

dhu%d: silo overflow.
The character input silo 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 may then print a message on the console with interrupts disabled.

 

NOTES

The driver currently does not make full use of the hardware capabilities of the DHU-11 for dealing with XON/XOFF flow-control or hard-wired lines for example.

Although the devices are not the same, a DHU-11 can convince the DH-11 autoconfiguration code that it is a DH-11

The 4 40-way cables are a pain.  

SEE ALSO

tty(4)  

HISTORY

The driver appeared in BSD 4.3


 

Index

NAME
SYNOPSIS
DESCRIPTION
FILES
DIAGNOSTICS
NOTES
SEE ALSO
HISTORY

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Time: 06:49:06 GMT, May 19, 2025