A delay-controlled phase-locked loop to reduce timing errors in synchronous/asynchronous communication links

Abstract

Asynchronous design techniques offer many advantages and are being increasingly used in digital systems. As a result, reliable synchronous/asynchronous communication links are needed. A handshaking protocol is often used in such links. However, errors due to metastability occur when a control signal changes too close to the active clock edge of the synchronous system. This paper introduces a simple, delay-controlled phase-locked loop that dynamically adjusts the timing of the control signals to avoid metastability. The proposed scheme is based on injecting a reference signal derived from the clock into the handshake loop. The injected signal induces changes in delay that provide the requisite feedback mechanism. Both simulation and experimental results are given in the paper. They show that stable operation can be achieved over a wide range of parameters.