DH

Section: Devices and Network Interfaces (4)
Updated: vax
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BSD mandoc
BSD 4  

NAME

dh - DH-11 / DM-11 multiplexer device interface  

SYNOPSIS

device dh0 at uba0 csr 0160020 vector dhrint dhxint [flags ] device dm0 at uba0 csr 0170500 vector dmintr [flags ]  

DESCRIPTION

A DH-11 provides 16 serial communication lines; DM-11 s may optionally be paired with DH-11 s to provide modem control for the lines.

An optional argument flags may be supplied with the device specification in the config(8) 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 dh0 would cause line ttyh2 to be treated in this way.

Normal I/O control parameters for individual lines are managed by ioctl(2) calls. Line speeds may be initiated via getty(8) and stty(1) or may be communicated by other programs which utilize ioctl such as ifcongif(8), see tty(4).

The dh driver monitors the rate of input on each board, and switches between the use of character-at-a-time interrupts and input silos. While the silo is enabled during periods of high-speed input, the driver polls for input 30 times per second.  

FILES

/dev/tty[h-o][0-9a-f]
/dev/ttyd[0-9a-f]

 

DIAGNOSTICS

dh%d: NXM.
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.

dh%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 will then print a message on the console with interrupts disabled. It is not serious.

 

SEE ALSO

tty(4)  

HISTORY

A driver appeared in AT&T System v6 .


 

Index

NAME
SYNOPSIS
DESCRIPTION
FILES
DIAGNOSTICS
SEE ALSO
HISTORY

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Time: 06:48:31 GMT, May 19, 2025