NSF-BSF: CNS Core: Small: Reliable and Zero-Power Timekeepers for Intermittently Powered Computing Devices via Stochastic Magnetic Tunnel Junctions

该项目致力于推动低功耗、无电池、能量采集的嵌入式系统在计时方面的最先进水平。这些系统必须在多次频繁断电的情况下执行计算和传感任务。这种间歇性操作需要强烈的时间感，以确保不浪费能量，计算结果不会过时。现有的计时器(即实时时钟)需要大量的能量来开启和操作，它们相对较大(毫米级)，重新启动很慢，并且使用的能量与电源故障的长度成比例(可能非常长)。该项目利用新兴的纳米级非易失性磁性随机存取存储器(MRAM)器件的独特特性，特别是可调节的数据保持长度，创造出功率更低、可调节的数量级超小型计时装置。系统可以设置计时器的几个比特，并在以后检查它们，以查看哪些比特丢失了信息。通过将每个比特或比特阵列定制为特定的时间长度，系统可以测量时间，而无论是否发生停电。这样的计时器需要相同的能量，如果它对一秒、一天或一年的停机进行计时，其精度取决于所使用的磁性元件的数量和特性。该项目跨越系统堆栈以实现计时器的好处；探索电路设计、体系结构和系统范例，以在间歇计算环境中嵌入这种新的计时设备：作为运行时时钟、中断源、数据和输入/输出(I/O)控制器的替代方案，以及作为即将到期的内存分配器。这些模块可供应用程序开发人员使用，以提高其程序的及时性。该项目中开发的技术将使一类重要的新兴计算机系统能够更有效和准确地计时。无电池和能量采集计算设备为物联网提供了更可持续的未来，并支持许多健康、农业和智能基础设施应用。取消远程供电传感器中的电池将缓解因电池磨损和更换而导致的日益增长的废品流。该项目的设备和系统的制造和最终分布将为未来的无电池系统提供更准确的计时模块，提高无电池系统的可靠性、安全性和及时性。由此产生的工具和实验结果将使无电池器件和磁存储器件的制造方法的稳健的跨堆栈模拟成为可能。该项目的成果将被整合到几个正在进行的外展活动中，让K-12和本科生接触嵌入式计算的使用和应用。这项工作将培训研究生在计算、材料和物理方面的基本技能，并通过GoBabyGo！让他们参与指导、教学和推广活动--学生们帮助有行动能力问题的儿童用骑乘玩具车制造电动轮椅。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project seeks to advance the state-of-the-art in timekeeping for low-power, battery-free, energy harvesting embedded systems. These systems must perform computation and sensing tasks across multiple, frequent power failures. This intermittent operation requires a strong sense of time to ensure no energy is wasted and computed results are not stale. Existing timekeepers (i.e. real-time clocks) require significant amounts of energy to turn on and operate, are relatively large (millimeter scale), are slow to restart, and use energy proportional to the length of a power failure (which can be impractically long). This project takes advantage of the unique properties of emerging nano-scale non-volatile magnetic random-access memory (MRAM) devices, particularly adjustable data retention length, to create orders of magnitude lower power, adjustable, ultra-small timekeeping devices. A system can set a few bits of the timekeeper and check them later to see which ones have lost information. By tailoring each bit, or array of bits, to particular lengths of time, the system can measure time regardless of whether a power failure occurred. Such a timekeeper requires the same amount of energy if it times an outage of one second, one day, or one year, with arbitrary accuracy depending on the number and characteristics of the magnetic elements used. The project cuts across the system stack to realize the benefits of this timekeeper; exploring circuit designs, architectural, and system paradigms to embed this new timekeeping device in the context of intermittent computing: as an alternative to a runtime clock, an interrupt source, a data and input/output (I/O) controller, and as an expiring memory allocator. These modules are made available to application developers to enhance the timeliness of their programs.The technologies developed in this project will enable more efficient and accurate timekeeping for an important emerging class of computer systems. Batteryless and energy harvesting computing devices offer a more sustainable future for the Internet of Things and enable numerous health, agriculture, and intelligent infrastructure applications. The elimination of batteries in remotely powered sensors will mitigate the growing waste stream resulting from battery wear out and replacement. The fabrication and eventual distribution of the devices and systems from this project will provide a more accurate timekeeping module for future batteryless systems, enhancing the reliability, security, and timeliness of batteryless systems. The resulting tools and experimental results will enable robust cross-stack simulation for battery-free devices and fabrication methods for magnetic memory devices. Outcomes of this project will be integrated into several ongoing outreach activities that expose K-12 and undergraduate students to the usage and application of embedded computing. This effort will train graduate students in essential skills across computing, materials, and physics and engage them in mentoring, teaching, and outreach activities via GoBabyGo!– where students help build power wheelchairs from ride-on toy cars for children with mobility issues.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.