HD66108 Datasheet, PDF (34/60 Pages) Hitachi Semiconductor – (RAM-Provided 165-Channel LCD Driver for Liquid Crystal Dot Matrix Graphics)

HD66108
5. Multiplexing Duty Ratio and LCD Driving Waveform Settings
A multiplexing duty ratio and LCD driving waveform can be selected via internal registers.
A multiplexing duty ratio of 1/32, 1/34, 1/36, 1/48, 1/50, 1/64, or 1/66 can be selected according to the
LCD panel used. However, since there are only 65 row-output pins, only 65 lines will be displayed even
if 1/66 multiplexing duty ratio is selected.
There are three types of LCD driving waveforms, as shown in Figure 22: A-type waveform, B-type
waveform, and C-type waveform.
The A-type waveform is called per-half-line inversion. Here, the waveforms of M signal and CL1 signal
are the same and alternate every LCD line.
The B-type waveform is called per-frame inversion; in this case, the M signal inverts its polarity every
frame so as to alternate every two LCD frames. This is the most common type.
The C-type waveform is called per-n-line inversion and inverts its polarity every n lines (n can be set as
needed within 1 to 31 via the internal registers). The C-type waveform combines the advantages of the A-
and B-types of waveforms. However, some lines will not be alternated depending on the multiplexing
duty ratio and n. To avoid this, another C-type waveform is available which is generated from the EOR of
the C-type waveform M signal mentioned above and the B-type waveform M signal. Since the
relationship between n and display quality usually depends on the LCD panel, n must be determined by
observing actual display results.
The B-type waveform should be used if the LCD panel specifies no particular type of waveform.
However, in some cases, the C-type waveform may create a better display.
LCD driving output pins
X0
X31 X32
X99 X100 X131 X132 X164
Block A
Block B
Block C
Block D
V1L V6L VMH1 VML1
V3 V4
VMH2 VML2
LCD driving power supply pins
VMH3 VML3 V6R V1R
Figure 21 Relationship between Blocks and LCD Driving Voltages
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