Intel® Quartus® Prime Standard Edition User Guide: Design Recommendations

ID 683323
Date 9/24/2018
Public
Download
Document Table of Contents

1.2.2.2. Avoid Asynchronous Clock Division

Designs often require clocks that you create by dividing a master clock. Most Intel FPGAs provide dedicated phase-locked loop (PLL) circuitry for clock division. Using dedicated PLL circuitry can help you avoid many of the problems that can be introduced by asynchronous clock division logic.

When you must use logic to divide a master clock, always use synchronous counters or state machines. Additionally, create your design so that registers always directly generate divided clock signals, and route the clock on global clock resources. To avoid glitches, do not decode the outputs of a counter or a state machine to generate clock signals.