My design is too fast!

Understanding hold-time violations across clock domains in FPGA design

This is a medium-difficulty question on static timing analysis (STA) and synchronization in FPGA design. It tests whether you understand the root cause of hold-time failures when data crosses between different clock domains, and how to apply the right remediation technique rather than just inserting delays blindly.

Hold-time violations occur when data arrives at a flip-flop's input too soon after the clock edge, preventing the register from capturing the intended value. When this happens at a clock-domain crossing, the issue is not just a timing slack problem—it reflects a fundamental synchronization risk. Fixing it requires understanding both the constraint semantics in your STA tool and the synchronization structures that prevent metastability.

• Clock-domain crossing (CDC) synchronization primitives
• Timing constraints and their role in CDC design
• False paths vs. timed paths in multi-clock domains
• Why simply adding delay is not a valid solution