ra8835 Topway Display, ra8835 Datasheet - Page 66

• Manufacturer Part Number: ra8835
• Description: Dot Matrix Lcd Controller
• Manufacturer: Topway Display

RAiO TECHNOLOGY INC.
Version 1.7
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.
The RA8835 series layered screens and flexible scrolling facilities support a range of display
functions and reduces the load on the controlling microprocessor when displaying underlining,
inverse display, text overlaid on graphics or simple animation.
These facilities are supported by the RA8835 series ability to divide display memory into up to four
different areas.
◎
◎
◎
◎
Character code table
Graphics data table
CG RAM table
CG ROM table
Contains character codes for text display
Each character requires 8 bits
Table mapping can be changed by using the scroll start function
Contains graphics bitmaps
Word length is 8 bits
Table mapping can be changed
Character generator memory can be modified by the external microprocessor
Character sizes up to 8x16-pixels (16 bytes per character)
Maximum of 64 characters
Table mapping can be changed
Used when the internal character generator is not adequate
Can be used in conjunction with the internal character generator and external
character generator RAM
Character sizes up to 8x16-pixels (16 bytes per character)
Maximum of 256 characters
Fixed mapping at F000H to FFFFH
66/86
Dot Matrix LCD Controller
www.raio.com.tw
RA8835