A Hardware-Assisted Approach for Non-Invasive and Fine-Grained Memory Power Management in MCUs

The energy demand of embedded systems is crucial and typically dominated by the memory subsystem. Off-the-shelf MCU platforms usually offer a wide range of memory configurations in terms of overall memory size, which may differ in the number of memory banks provided. Split memory banks have the potential to optimize energy demand, but this often remains unused in available hardware due to a lack of power management support or require significant manual effort to leverage the benefits of split-banked memory architectures. This paper proposes an approach to solve the challenge of integrating fine-grained power management support automatically, by a combined hardware/software solution for future off-the-shelf platforms. We present a method to efficiently search for an optimized code and data mapping onto the modules of split memory banks to maximize the idle times of all memory modules. To non-invasively put memory modules into sleep mode, a PC-driven power management controller (PMC) autonomously triggers transitions between power modes during embedded software execution. The evaluation of our optimization flow demonstrates that memory mappings can be explored in seconds, including the generation of the necessary PMC configuration and linker scripts. The application of PC-driven power management enables active memory modules to remain in light sleep mode for approximately 13% to 86% of the execution time, depending on the workload and memory configuration. This results in overall power savings of up to 24% in the memory banks, in terms of static and dynamic power.