Description - Epson SED1352 Technical Manual

Epson Research and Development
Vancouver Design Center

5.1.2 Description

The SED1352 can be programmed to use memory offsets in such a way that the physical display behaves as a viewport into
a much larger "virtual" memory space. This viewport can be panned and/or scrolled to display this larger memory space.
Referring to the figure below, a virtual image of 640x480 can be viewed by navigating the 320x240 viewport around the
image by panning and scrolling
.
To create a virtual display, the Address Pitch Adjustment Register must be programmed to indicate the horizontal size of
the larger, "virtual" image stored in display memory. The Address Pitch Adjustment Register tells the SED1352 how many
bytes or words of display memory are part of the nonvisible region of display memory (see Example 10).
Example 10: Program the Address Pitch Adjustment Register to support a 16 gray shade 640x480
virtual display on a 320x240 LCD panel; the Memory Interface is 16 bits.
1. Initialize the SED1352 registers for a 320x240 panel.
2. Determine whether the Address Pitch Adjustment Register refers to bytes or words.
Since the Memory Interface is set to 16 bits, the Address Pitch Adjustment Register refers to words.
3. Determine the number of pixels per unit referred to by the Address Pitch Adjustment Register.
The Address Pitch Adjustment Register refers to units of words, so find the number of pixels per word.
4. Calculate the number of pixels on a horizontal scan line not visible.
(
virtual display width in pixels
Consequently on a screen update the SED1352 will show the first 320 of 640 pixels, and then ignore the remaining
320 pixels in order to reach the next scan line.
5. Program the Address Pitch Adjustment Register:
Therefore AUX[0Dh] = 50h
6. To view the rest of the image refer to Section 5.5, "Panning and Scrolling" on page 42, keeping in mind that the hor-
izontal width is 640 pixels, not 320.
Programming Notes and Examples
Issue Date: 98/10/08
320x240
Viewport
Figure 8: 640 x 480 Virtual Display
16 gray shades => 4 bits per pixel
4 bits per pixel => 2 pixels per byte
(
pixels per word = pixels per byte
) (
– panel width in pixels
number of hidden horizontal pixels
----------------------------------------------------------------------------------- -
pixels per word
640x480
"Virtual" Display
) 2 × ×
= 2 2 = 4 pixels per word
)
= 640 320 – =
320
= -------- - = 80 words = 50h words
4
320 hidden pixels
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SED1352