Graphic adapters and monitors –
the summary
1
Outline
• The summary of principles of displaying the information
– adapters and monitors.
• Black and white monitors.
• Digital monitors.
• Analog monitors.
• LCD monitors and analog interface.
• LCD monitors and DVI interface.
2
How CRT monitor is constructed?
CRT – Cathode Ray Tube Controller
This is the situation in black and white monitor – one electron beam.
Color monitor – three electron beams.
3
The image on screen – how it works?
• Black and white monitor (mono monitor) – just two colors
are displayed.
• Information about color is stored in video memory as „0“
and „1“.
• This information is transported to monitor as analog
signal.
• The voltage is brought to anode, the beam of electrons is
either accelerated (the fluorescent layer at this dot is
illuminated) or not (the fluorescent layer at this dot is not
illuminated)
• The levels of grey color – not only two values of voltage
are available, but more values. The number of analog
values depends on the number of bits used to represent
the information about the dot color. The digital value is
converted into analog voltage which is transported to
monitor and its anode.
4
The image on screen – mono monitor
Grapfic
adapter
Video memory: 0/1
(dot is
illuminated/is not
illuminated
System bus
cable
monitor
Cable: 0/1 voltage
The consequence: the dots on monitor are
illuminated/are illuminated according to
the information brought from video
memory
Typical for text mode.
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The image on screen – mono monitor (graphics)
Grapfics
adapter
Video memory:
several bits 0/1 for
each pixel
System bus
cable
monitor
analog voltage
Analog voltage – it is generated in graphics
adapter by converting binary representation
of the pixel color (in fact level of grey color)
to the analog voltage transported through
the cable to monitor.
With this voltage applied to anode, the beam of electrons is accelerated
– different voltage – different energy with which the beam of electrons
hits the fluorescent layer (pixel)on the screen – different intensity of
pixel.
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The image on screen – color monitor (digital control)
Graphics
adapter
cable
monitor
Cable: 0/1 for each
color R,G,B
Video memory: 0/1
(the pixel lights/does not light),
this information is available for
each color R,G, B
System bus
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The image on screen – color monitor (analog control)
Graphics
adapter
Cable: analog
voltage for each
color R,G,B
cable
monitor
System bus
Video memory: certain number
of bits 6/8/ …. for each color
R,G,B
The conversion to analog
voltage – for each color R, G, B
one DAC is needed
8
Graphics
adapter
cable: 3 color
components, the
information is
transported serially in
digital form
cable
monitor
LCD monitor, DVI interface
The reasons for serial interface: faster communication, wider
bandwidth, higher resolution.
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