Online Test Vector Insertion: A Concurrent Built-In Self-Testing (CBIST) Approach for Asynchronous Logic

TL;DR

This paper introduces a novel online testing method for asynchronous circuits that uses the 4-phase protocol's NULL phase to interleave test vectors, enabling transparent and concurrent testing with moderate overhead.

Contribution

It proposes a new approach leveraging the 4-phase protocol's NULL phase for fully concurrent, non-intrusive online testing of asynchronous circuits, addressing a key challenge in the field.

Findings

Moderate overhead in test implementation

Successful proof-of-concept demonstration

Effective interleaving of test data with normal operation

Abstract

Complementing concurrent checking with online testing is crucial for preventing fault accumulation in fault-tolerant systems with long mission times. While implementing a non-intrusive online test is cumbersome in a synchronous environment, this task becomes even more challenging in asynchronous designs. The latter receive increasing attention, mainly due to their elastic timing behaviour; however the issues related with their testing remain a key obstacle for their wide adoption. In this paper we present a novel approach for testing of asynchronous circuits that leverages the redundancy present in the conventional 4-phase protocol for implementing a fully transparent and fully concurrent test procedure. The key idea is to use the protocol's unproductive NULL phase for processing test vectors, thus effectively interleaving the incoming 4-phase data stream with a test data stream in a 2-phase fashion. We present implementation templates for the fundamental building blocks required and give a proof-of-concept by an example application that also serves as a platform for evaluating the overheads of our solution which turn out to be moderate.