Energy-Efficient Flash Memory Management in Embedded Systems

Abstract: In today’s embedded systems there is a growing need for energy efficient solutions as applications and hardware are growing in power consumption levels. That is why GEODES was initiated, a project where several companies and universities hold as main objective to develop power efficient solutions in embedded software. This master thesis is realized at ENEA and is part of GEODES. The focus of the work is flash memory management and how this type of software can be made power efficient. The first part of the master thesis is a theoretical study in flash memory management and power efficiency in flash systems. This study identified and evaluated the current solutions that exist in this topic. The theoretical foundation was made so an implementation of an energy efficient flash management system could be realized. A requirement specification was also developed regarding both basic functionality and energy optimization. After the theoretical study a power efficient design was developed, containing techniques like data separation, intelligent garbage collection and the utilization of a cache memory. More basic functionality like error code correction, bad block management and wear levelling was also included. The implementation was based on this design and the result was a driver layer for a flash memory, however no power management techniques were included due to time restrictions. The driver was implemented on an i.MX31 board in an OSE5.4 environment; this module (memory device driver - MDD) controlled a 128 M x 8-bit NAND flash memory and included functionalities such as error code correction, bad block management and status read. The MDD utilized an internal RAM buffer and the i.MX31 boards NAND flash controller. It executed all the operations (read, write and erase) and used the spare area for metadata writes.