Power-Aware Bus Encoding Techniques for I/O and Data Buses in an Embedded System

Microprocessors with built-in Liquid Crystal Device (LCD) controllers and equipped with Flash ROM are common in mobile computing applications. In the first part of the paper, a software-only encoding technique is proposed to reduce the power consumption of the processor-memory bus when displaying an image on the LCD. Based on the translation mechanism of the LCD controller, the approach of this paper is to start with the palette as a coding table for the pixel buffer and then reassign the codes according to the image characteristics. Experimental results prove the efficacy of this approach; power reduction reaches 29% for text-based and 17% for graphics-based images. In the second part of the paper, another software-only encoding technique is presented to reduce the transitions on the processor-CompactFlash bus. The device driver in a Linux operating system is modified to perform Bus-Invert encoding when the data is read from or written to a Compact Flash file system. With minimal software overhead, the transitions on the bus are reduced by up to 25%.