hd66717 Renesas Electronics Corporation., hd66717 Datasheet - Page 64

• Manufacturer Part Number: hd66717
• Description: Low-power Dot-matrix Liquid Crystal Display Controller/driver -
• Manufacturer: Renesas Electronics Corporation.

HD66717
Vertical Smooth Scroll
The HD66717 can scroll in the vertical direction in units of raster-rows. This function is achieved by
writing character codes into the DDRAM area that is not being used for display. In other words, since the
DDRAM corresponds to a 5-line
12-character display, one of the lines can be used to achieve
continuous smooth vertical scroll even in a 4-line display. Here, after the fifth line is displayed, the first
line is displayed again. Specifically, this function is controlled by incrementing or decrementing the
value in the scroll-start line bits (SL2 to SL0) and scroll-start raster-row bits (SN2 to SN0) by 1. For
example, to smoothly scroll up, first set SN2 to SN0 to 000, and increment SL2 to SL0 by 1 from 000 to
111 to scroll seven raster-rows. Then increment SN2 to SN0 to 001, and again increment SL2 to SL0 by 1
from 000 to 111. To start displaying and scrolling from the first raster-row of the second line, update the
first line of DDRAM data as desired during its non-display period.
Figure 38 shows an example of vertical smooth scrolling and Figure 39 shows an example of setting
instructions for vertically scrolling upward in a 4-line display (NL1 and NL0 = 11).
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