CDC-50008: CDC Bus Constructed with Multi-bit Synchronizer Chains

Description

Violations of this rule identify multi-bit synchronizer chains that form a CDC bus. This CDC topology is only valid for buses that transfer Gray-coded data.

Figure 1. Synchronized CDC Bus Transfer.. The following figure shows a synchronized CDC bus transfer, which must be Gray-coded to work correctly:

Recommendation

If the bus does not transfer Gray-coded data, change its implementation to incorporate a control signal since synchronizer chains are not sufficient to ensure that all bits of the bus latch on the same clock cycle.

This violation can be waived if the bus transfers Gray-coded data.

Severity

Low

Tags

Tag Description
synchronizer  
cdc-bus  

Device Family

  • Intel® Cyclone® 10 GX
  • Intel® Arria® 10
  • Intel® Stratix® 10
  • Intel® Agilex™