Energy-efficient bus encoding for LCD digital display interfaces

This paper presents a low-power encoding technique explicitly devised for the digital interface to liquid crystal displays (LCDs). The proposed code, called limited intra-word transition (LIWT), exploits the existing inter-pixel correlation of typical images, by selectively transmitting a suitably encoded representation of the difference between adjacent pixels. Since all LCD transmission protocols are serial, the LIWT code specifically targets the reduction of intra-word transitions by defining codewords with limited intra-word transition counts. Three are the main improvements of the proposed code with respect to previous solutions. First, it provides superior energy; savings at a reduced complexity; second, it can adapt to the different signaling schemes of standard protocols; third, it can account for DC-balancing without requiring additional logic to implement it, The application of the encoding to a series of standard images resulted in transition savings over 60% on average with respect to the TMDS, LVDS and GVIF protocols. A DC-balanced version of the encoding achieves almost perfect balancing, with only a 2% reduction of the transition savings.