qv.4

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)qv.4	8.1	9/11/90
.TH qv 4 VAX
.SH Name
qv \- VCB01 (QVSS) video subsystem
.SH Syntax
.B "device qv0 at uba0 csr 0177200 flags 0x0f  vector qvkint qvvint"
.SH Description
.NXS "qv interface" "VCB01 video subsystem"
.NXR "VCB01 video subsystem"
.NXR "console terminal" "QVSS and"
.NXS "QVSS" "VCB01 video subsystem"
A VCB01 provides a half-page or
full-page, user-accessible bitmap display for
graphics applications.
The device consists of a 256 kbyte 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 VCB01
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 VCB01
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 Restrictions
The use of the bitmap as source or destination of I/O operations is not
supported.
Minor devices 1 and 2 are read only and are the only ones supported by
the MAKEDEV script.
Shared access by multiple processes is not constrained or supported.
The system only supports one VCB01.
The mouse device buffers the last 50 events (state changes).
If the console port has been enabled as an additional terminal it must
be disabled before removing the
VCB01 to avoid two login processes on the same device.
.SH Files
.PN /dev/qvscreen
.br
.PN /dev/mouse
.SH See Also
tty(4), ttys(5), MAKEDEV(8)