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Epson Research and Development
Vancouver Design Center
4 Advanced Technique s
4.1 Virtual Display
Programming Notes and Examples
Issue Date: 01/02/01
This section presents information on the following:
• virtual display
• panning and scrolling
• split screen display
A virtual display is when the image to be displayed is larger than the physical display device in either
the horizontal dimension, the vertical dimension, or both. To view the image, the physical display is
used as a window or viewport into the display buffer, allowing the user to see a portion of the entire
image. This viewport can be panned and scrolled, enabling the user to view the entire image.
The size of the virtual display is limited by the amount of available display buffer. In the case of an
S1D13504 with 2M byte of display buffer, the maximum virtual width ranges from 16,368 pixels in
1 bpp mode to 1023 pixels in 16 bpp mode. The maximum vertical size at the horizontal maximum
is 1025 lines. By trading off horizontal size a greater vertical size can be achieved.
Seldom are the maximum sizes required. Figure 4-1: "Viewport Inside a Virtual Display," depicts
a more typical use of a virtual display. An image of 640x480 pixels can be viewed by navigating a
320x240 pixel viewport around the image using panning and scrolling.
320x240
Viewport
Figure 4-1: Viewport Inside a Virtual Display
640x480
"Virtual" Display
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