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Epson Research and Development
Page 135
Vancouver Design Center
Hardware Functional Specification S1D13505
Issue Date: 01/02/02 X23A-A-001-14
13 SwivelView™
13.1 Concept
Computer displays are refreshed in landscape – from left to right and top to bottom; computer images
are stored in the same manner. When a display is used in SwivelView it becomes necessary to rotate
the display buffer image by 90
°
. SwivelView rotates the image 90
°
clockwise as it is written to the
display buffer. This rotation is done in hardware and is transparent to the programmer for all display
buffer reads and writes.
SwivelView uses a 1024
×
1024 pixel virtual image. The following figures show how the
programmer sees the image and how the image is actually stored in the display buffer. The display
is refreshed in the following sense: C–A–D–B. The application image is written to the S1D13505 in
the following sense: A–B–C–D. The S1D13505 rotates and stores the application image in the
following sense: C–A–D–B, the same sense as display refresh.
Figure 13-1: Relationship Between The Screen Image and the Image Residing in the Display Buffer
Note
The image must be written with a 1024 pixel offset between adjacent lines (e.g. 1024 bytes for
8 bpp mode or 2048 bytes for 16 bpp mode) and a display start address that is non-zero.
1024 pixels
1024 pixels
image seen by programmer
image in display buffer
1024 pixels
portrait
window
W
H
AB
C
D
AB
C
D
H
W
start
address
portrait
window
display