Circuit and method for testing whether a programmable logic device complies with a zero-hold-time requirement

摘要

Described are a system and method for quickly and accurately testing sequential storage elements on programmable logic devices for zero-hold-time compliance. A programmable logic device is configured such that both the data and clock terminals of a selected sequential logic element connect to an input pin of the programmable logic device and the output terminal of the sequential logic element connects to an output pin of the programmable logic device. A circuit tester connected to the input pin then generates a signal transition on the input pin so that the signal transition traverses both the data and clock paths in a race to the sequential storage element. The circuit tester also includes an input terminal that monitors the PLD output pin to determine whether the storage element contains the correct data after the storage element is clocked. Incorrect data stored in the sequential storage element after the storage element is clocked indicates that the clock signal arrived before the data, and therefore that the selected storage element violated the zero-hold-time requirement in the specified configuration.