qd.4

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)qd.4	8.1	9/11/90
.TH qd 4 VAX
.SH Name
qd \- VCB02 (QDSS) video subsystem
.SH Syntax
.B "device qd0 at uba0 csr 0177400 flags 0x0f  vector qddint qdaint qdiint"
.SH Description
.NXS "qd interface" "VCB03 video subsystem"
.NXR "VCB03 video subsystem"
.NXS "QDSS" "VCB02 video subsystem"
A VCB02 provides a half-page or full-page user-accessible 
bit map display for
graphics applications.
The device consists of a 256kb Q22 bus memory array,
a 15-inch or 19-inch video monitor, and a VX10X-EA mouse.
.PP
The subsystem device driver supports
a hybrid terminal with three minor devices.
The first device emulates a glass tty with a
screen that appears as a 120-column
by 80-row page that scrolls from the bottom.
This device is capable of being configured as the system console.
.PP
The second minor device is opened in the raw mode by default.
Opening the second device makes the driver function like a pseudoterminal
in that the output destined for the first minor device is channeled to
the second instead.
Input and output on the first two minor device numbers are processed by
the standard line disciplines.
.PP
The third minor device number is reserved for the mouse.
This device is a source of mouse state changes.
(A state change is defined as an X/Y axis
mouse movement or button change.)
When opened, the driver couples movements of the mouse with the cursor.
Mouse position changes are filtered and translated into cursor position
changes in an exponential manner.
Rapid movements result in large cursor position changes.
All cursor positions are range checked to ensure that the 
cursor remains on the display.
.PP
If there is a VCB02
module at the standard address, the system will use it as
the system console.
All input/output destined for 
.PN /dev/console
will use the VCB02 instead.  
(This is done by overwriting the device switch tables.)
There is a second set of device switch entries
configured for the console
that can be used as an additional terminal or printer port
by making a special device file using major number 38 and minor number 0
and making the appropriate entry in 
.PN /etc/ttys .
.SH Files
.PN /dev/qd?
.br
.PN /dev/qconsole
.SH See Also
tty(4), ttys(5), MAKEDEV(8)