Testable MUTEX Design

The mutual exclusion element is a fundamental component of asynchronous arbiters. Despite their importance, however, the testability of these components is typically limited to functional testing. This paper discusses why this is not sufficient and investigates three MUTEX implementations, two of which are completely new, that support the test of the metastability filter part of the components. Additionally, we quantify the cost of the testable designs by comparing them to a baseline design in terms of failure rate, impact on MTBF, propagation delay, test power and area. Our experimental results show that testable MUTEXes increase area from 21% to 63% over the baseline implementation, but have a small impact on delay and provide a range of choices where testability, MTBF, test power and area can be traded-off against circuit and system requirements.