Clock Domain Crossing Tools – Reviews & Metrics

What is Clock Domain Crossing?

A clock domain crossing is when data is transferred from a flop driven by one clock domain to a flop driven by another clock domain. Because different clock domains don’t have a defined phase relationship, there can be problems transferring data from the source clock to the destination clock.

What is CDC Metastability?

Signal metastability can occur when a signal crossing from one clock domain to another clock domain and arrives too close to the receiving clock edge. Since the CDC signal can fluctuate, This can potentially cause illegal signal values to propagate through the design.

Clock Domain Crossing

What is CDC Sign Off?

Clock domain crossing sign off requires analysis, debug, modifications and verification that the data is properly transferred across clock domains, without introducing design problems.

Clock Domain Crossing Reviews

There are multiple commercial tools that will address CDC analysis and verification throughout the design process. Below are detailed user reviews on the most commonly used clock domain crossing tools from annual EDA user reports. The most recent report was released in early 2019.

The products reviews include: Real Intent Meridian CDC & Synopsys SpyGlass CDC.

CDC Product Metrics

Below are the primary metrics and criteria that the system and semiconductor verification engineers referenced when reviewing the products.

CDC Tool Metrics Covered

  • Sign-off methodology customizability
  • Noise level in CDC violation reporting
  • Debug usability, visibility and  drilldown
  • Performance & Capacity
  • CDC analysis depth
  • Set up time

Multimode CDC Tool Metrics Covered

  • Sign-off quality, including fit with STA sign-off
  • Low noise
  • Common report with no duplicates to save CDC violation debug time
  • Modeling & constraining the design for complex clocking structures
  • Set up time & Capacity