
P.34
Panel Controller
The Panel Controller redefines data format from Attribute Controller in LCD/PLASMA/EL dis-
play modes. The TP6508 can directly drive various flat panels, including dual-scan/single-scan mono-
chrome, color STN, and color TFT.
For monochrome LCD/PLASMA/EL panels, it converts FP0-FP7 to gray level and goes through a
special functional operation, sum_to_gray, which is called Gray Scaling. For color LCD panels, it
converts FP0-FP23 to R.G.B. color level and goes through two special functional operation, which are
called Dithering and Amplitude modulation .
The VGA standard defines how colors are mapped to 64 gray scale values on monochrome moni-
tors. The mapping is based on the following weighting equation:
I=0.30R+ 0.59G+ 0.11B
This formula follows the NTSC conversion standard and is confirmed to display the original
color information.
Basically, monochrome flat panels do not actually show shades of gray, but only black and white.
To build a gray scale, some pixels stay white proportionally longer than they are dark, depending on
the shade of gray being built up. Gray scaling ( pattern modulation ) techniques determine which pixels
are white or dark for corresponding gray level. If not done well, “Flicker” and “ripples” will occur.
Others, the gray scaling techniques also can be using for color flat panel display. Of course it
will be occurred on color STN LCD panels that those problems are talking in previous paragraph. The
TP6508 controller support both 8 and 16 bit interfaces to STN panels; 9-bit /12-bit/15-bit or 18-bit/
24-bit interface TFT color LCD panels.
In addition, 65536 simultaneous colors are supported for color STN LCD panels, and up to
226,981 visual colors are supported by color dithering techniques. For color TFT LCD panels, TP6508
can support 16.8M simultaneous colors on 24-bit interface. Further more, 512 simultaneous colors are
supported for 9-bit interface color TFT LCD panels, and up to 185,193 visual colors are supported by
amplitude modulation techniques.
To avoid flicker and ripple phenomenon. There are three approaches:
(1) increase frame rate:
The higher the switching rate, the better the display quality.
(2) adequate modulation sequences:
Spread pixels frame ON time on continuous “timing”.
(3) dispersion modulation:
Enhance modulation task from time spreading to spatial spreading each pixel on/off ratio does
not change, but has “time shift for neighboring pixels.