HD66727 Datasheet, PDF (72/97 Pages) Hitachi Semiconductor – Low-Power Dot-Matrix Liquid Crystal Display Controller/Driver with Key Scan Function

HD66727
Vertical Smooth Scroll
The HD66727 can scroll in the vertical direction in units of raster-rows. This function is achieved by
writing character codes into DDRAM area that is not being used for display. In other words, since 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 display-start line
bits (SL2 to SL0) and display-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 41 shows an example of vertical smooth scrolling and Figure 42 shows an example of setting
instructions for vertically scrolling upward in a 4-line display (NL1 and NL0 = 11).
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