ra8835a RAIO Technology Inc., ra8835a Datasheet - Page 71

• Manufacturer Part Number: ra8835a
• Description: Dot Matrix Lcd Controller
• Manufacturer: RAIO Technology Inc.

RAiO TECHNOLOGY INC.
Version 1.0
8-4 Smooth Horizontal Scrolling
Figure 8-7 illustrates smooth display scrolling to the left. When scrolling left, the screen is effectively
moving to the right, over the larger virtual screen. Instead of changing the display start address SAD
and shifting the display by eight pixels, smooth scrolling is achieved by repeatedly changing the pixel-
shift parameter of the HDOT SCR command. When the display has been scrolled seven pixels, the
HDOT SCR pixel-shift parameter is reset to zero and SAD incremented by one. Repeating this
operation at a suitable rate gives the appearance of smooth scrolling.
To scroll the display to the right, the reverse procedure is followed. When the edge of the virtual screen
is reached, the microprocessor must take appropriate steps so that the display is not corrupted. The
scroll must be stopped or the display modified.
Note that the HDOT SCR command cannot be used to scroll individual layers.
Note: The response time of LCD panels changes considerably at low temperatures. Smooth scrolling
under these conditions may make the display difficult to read.
SAD=SAD+1
SAD=SAD
HDOT SCR
parameter
P1=00H
P1=01H
P1=02H
P1=03H
P1=07H
P1=00H
Not visible
Figure: 8-7 HDOT SCR Example
SAD
Visible
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SAD+1
SAD+2
Magnified
Virtual screen
C/R
Display
Dot Matrix LCD Controller
AP
RA8835A
www.raio.com.tw