GMS30C7201 Datasheet, PDF (133/352 Pages) Hynix Semiconductor – 60MHz operation frequency Low power consumption

LCD & VGA Controllers
11.2.4 Color/Grayscale Dithering
Entries selected from the look-up palette are sent to the color/grayscale space/timebase dither
generator. Each 4-bit value is used to select one of 15 intensity levels. Note that two of the 16
dither values are identical. The table below assumes that a pixel data input to the LCD panel is
active HIGH. That is, a ‘1’ in the pixel data stream will turn the pixel on, and a ‘0’ will turn it
off. If this is not the case, the intensity order will be reversed, with “0000” being the most
intense color. This polarity is LCD panel-dependent.
The gray/color intensity is controlled by turning individual pixels on and off at varying periodic
rates. More intense grays/colors are produced by making the average time that the pixel is off
longer than the average time that it is on. The proprietary dither algorithm is optimized to
provide a range of intensity values that match the eye’s visual perception of color/gray
gradations, with smaller changes in intensity nearer to the mid-gray level, and greater nearer the
black and the white levels. In color mode, red, green and blue components are gray-scaled
simultaneously as if they were mono pixels.
The duty cycle and resultant intensity level for all 15 color/grayscale levels is summarized in
Table 11-1: Color/grayscale intensities and modulation rates.
11.2.5 TFT mode
Dither Value
(4-bit value from palette)
Intensity
Modulation Rate
(0% is white) (ratio of ON to ON+OFF pixels)
0000
0.0%
0
0001
11.1%
1/9
0010
20.0%
1/5
0011
26.7%
4/15
0100
33.3%
3/9
0101
40.0%
2/5
0110
44.4%
4/9
0111
50.0%
1/2
1000
55.6%
5/9
1001
60.0%
3/5
1010
66.6%
6/9
1011
73.3%
11/15
1100
80.0%
4/5
1101
88.9%
8/9
1110
100.0%
1
1111
100.0%
1
Table 11-1: Color/grayscale intensities and modulation rates
When TFT display mode is enabled, the timing of the pixel, line and frame clocks as well as the
AC-bias pin change. The pixel clock transitions continuously in this mode as long as the LCD
is enabled. The AC-bias pin functions as an output enable. When it is HIGH, the display latches
data from the LCD’s pins using the pixel clock. The line clock pin is used as the horizontal
GMS30C7201 Data Sheet
11-5