Intel® Quartus® Prime Pro Edition User Guide: Getting Started

ID 683463
Date 3/28/2022

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3.11.3. Managing Metastability

Metastability problems can occur in digital design when a signal is transferred between circuitry in unrelated or asynchronous clock domains, because the designer cannot guarantee that the signal meets the setup and hold time requirements during the signal transfer.

Designers commonly use a synchronization chain to minimize the occurrence of metastable events. Ensure that your design accounts for synchronization between any asynchronous clock domains. Consider using a synchronizer chain of more than two registers for high-frequency clocks and frequently-toggling data signals to reduce the chance of a metastability failure.

You can use the Intel® Quartus® Prime software to analyze the average mean time between failures (MTBF) due to metastability when a design synchronizes asynchronous signals, and optimize your design to improve the metastability MTBF. The MTBF due to metastability is an estimate of the average time between instances when metastability could cause a design failure. A high MTBF (such as hundreds or thousands of years between metastability failures) indicates a more robust design. Determine an acceptable target MTBF given the context of your entire system and the fact that MTBF calculations are statistical estimates.

The Intel® Quartus® Prime software can help you determine whether you have enough synchronization registers in your design to produce a high enough MTBF at your clock and data frequencies.

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