HD66730 Datasheet, PDF (94/131 Pages) Hitachi Semiconductor – Dot-Matrix Liquid Crystal Display Controller/Driver Supporting Japanese Kanji, Korean Font Display

HD66730/HD66731
Horizontal Smooth Scroll
Data shown on the display can be scrolled horizontally to the left for a specified number of dots (Figure
28). The number of dots are set in scroll control register 3 (SCR3: R7), and the display lines to be scrolled
are designated by the display line enable bits (SE1/SE2/SE3/SE4) in scroll control register 2 (SCR2: R6).
Because the number of dots that can be set for scrolling here is 48, scrolling for more than this number can
be achieved by shifting to the left by four characters of character code data in DDRAM for the scroll
display line in question, rewriting the characters, and then scrolling again. When rewriting DDRAM while
displaying characters, however, character output will momentarily breakdown, and the display may flicker.
In this case, first check which display lines are currently being displayed by referring to NF1/0 (line 1 to
the line 4) and display raster-rows LF0 to LF3 (raster-row 1 to raster-row 13) in the status register, and then
rewrite a DDRAM line that is not being displayed. Keep in mind that scroll display line enable bits (SE1 to
SE4) can be used to designate those display lines for which horizontal smooth scroll is desired.
In partial scroll, one to three leftmost characters on the display as specified by the partial scroll bits (PS1/0)
of the scroll control register 2 (SCR: R6) are fixed and the remaining characters undergo a smooth scroll to
perform partial smooth scroll.
When performing horizontal smooth scroll, the number of characters to be displayed (NC1/0: R4) must be
at least 4 characters more than the number of characters actually displayed on the liquid crystal display. For
example, set 10 or more display characters (NC1/0) for a single-chip 6-character display.
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