Intel® Quartus® Prime Pro Edition User Guide: Platform Designer

ID 683609
Date 10/04/2021
Public

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4.5.1.2. Using Clock Crossing Bridges

The clock crossing bridge contains a pair of clock crossing FIFOs, which isolate the host and agent interfaces in separate, asynchronous clock domains. Transfers to the agent interface are propagated to the host interface.

When you use a FIFO clock crossing bridge for the clock domain crossing, you add data buffering. Buffering allows pipelined read hosts to post multiple reads to the bridge, even if the agents downstream from the bridge do not support pipelined transfers.

You can also use a clock crossing bridge to place high and low frequency components in separate clock domains. If you limit the fast clock domain to the portion of your design that requires high performance, you may achieve a higher fMAX for this portion of the design. For example, the majority of processor peripherals in embedded designs do not need to operate at high frequencies, therefore, you do not need to use a high-frequency clock for these components. When you compile a design with the Intel® Quartus® Prime software, compilation may take more time when the clock frequency requirements are difficult to meet because the Fitter needs more time to place registers to achieve the required fMAX. To reduce the amount of effort that the Fitter uses on low priority and low performance components, you can place these behind a clock crossing bridge operating at a lower frequency, allowing the Fitter to increase the effort placed on the higher priority and higher frequency datapaths.