Research To LCD Greyscale Modulation And Frame Buffer Compress Technique

With the technical development of LCD (Liquid Crystal Display) and it's price descent,the LCD show its application in daily life more and more widely. Aim at the requirement ofLCD in hand-held device, in this paper we introduce two key technologies: 1) the greyscalecontrolling technique applied in the greyscale and the CSTN(Color Super Twisted Nematic)display: the FRC(Frame Rate Control) greyscale controlling arithmetic. 2) Aim at the fact thatLCD controller occupies too much bandwidth, a technology called frame buffer compress isintroduced, which reduces the bandwidth required by display.At first, we introduce some background knowledge, the architecture of Garfield and atypical display system, based on this, the design of LCD controller. The greyscale display andthe CSTN display are much more cheaper and consume less power compared with the TFTdisplay, so they have a good chance of being well-received in the low price market. Thegreyscale modulation is the key of these two display patterns, we introduce the mechanism ofgreyscale modulation and several greyscale modulating methods. After we compared themwith each other, we put great emphasis on the introduction of FRC greyscale modulatingarithmetic as well as it's realization. The FRC greyscale modulation can display an averagegreyscale of an image without the degrease of color steps neither flicker and dithering.Wehave applied the FRC greyscale modulation in our chip-"Garfield5"and the result turned tobe ok.Besides, High resolution and large bpp(bits-per-pixel) color LCD display occupies toomuch bandwidth which influences the performance of our system. At the same time, therequirement of low power consumption needs low power design of the display system. Toreduce the bandwidth of LCD controller and the number of memory accessing times withoutloss of image quality, in the second part of this paper, a technique called frame buffercompress is introduced, as well as its realization. Besides, the test platform and the evaluationare also given. In interactive applications, by using frame buffer compress technique in boththe 16bpp TFT display mode and 12bpp CSTN display mode, the bandwidth of LCDcontroller can be reduced to 65％and 45％respectively, and the power consumption ofSDRAMcan be reduced to 70％and 60％respectively. Better results will be achieved inhigher resolution display.