Synchronous-Logic and Asynchronous-Logic 8051 Microcontroller Cores for Realizing the Internet of Things: A Comparative Study on Dynamic Voltage Scaling and Variation Effects

Microcontrollers play a vital role in embodying intelligence into battery-powered everyday objects to realize the internet of things (IoT). The desirable attributes of such a microcontroller and the like include high energy and area efficiency, and robust error-free operation under dynamic voltage scaling (DVS), workload, process, voltage, and temperature (PVT) variation effects. In this work, a synchronous-logic$(S 8051)$and a quasi-delay-insensitive asynchronous-logic$(A 8051)$8051 microcontroller core are designed and fabricated for full-range DVS from nominalVDDto deep sub-threshold. The performance of the$S 8051$and$A 8051$are largely comparable at nominal conditions and the entire DVS range, but differs when PVT and workload are varied. At nominalVDD, both the microcontroller cores feature comparable energy and speed, with the electromagnetic interference of theA 8051 \! ~ \! \! \! 12~ dBlower and the area~2×larger than the$S 8051$. When DVS is applied, both the microcontroller cores feature comparable energy and speed; the$S 8051$requires simultaneous adjustment of clock frequency withVDD. At wide PVT variations, up to~12×delay margins are required for the$S 8051$, whereas the$A 8051$operates at actual speed. When the workload of both microcontrollers is varied, the$A 8051$features lower energy dissipation per workload due to the exploitation of its asynchronous-logic protocols. For IoT applications that incur wide PVT and workload variations,$A 8051$is more suitable due to its self-timed nature, whereas when PVT and workload variations are less severe,$S 8051$is more suitable due to a smaller IC area.