Blocking assignments (=) are typically suitable for describing combinational logic. However, using blocking assignments in sequential logic—especially when there are multiple assignments within the same always procedural block—can cause synthesis mismatches.

This happens because in a blocking assignment, each statement must complete before the next one executes. As a result, the hardware representation may be incomplete or inaccurate, producing undesired behavior.

✅ Recommendation: Avoid blocking assignments in sequential logic to prevent unintended synthesis results.

Nonblocking assignments (<=) are essential for modeling sequential logic in Verilog RTL. These assignments are evaluated concurrently within the active and NBA (Nonblocking Assignment) queues.

Using nonblocking assignments inside always blocks ensures that multiple operations execute in parallel, allowing the synthesis tool to correctly infer flip-flop behavior. This concurrent execution aligns with the actual behavior of clocked digital circuits.

✅ Recommendation: Always use nonblocking assignments when designing sequential logic blocks.

A crucial topic for ASIC design engineers is when and how to use resets in a design. There are two main types of resets:

• Synchronous Reset: Triggered on the clock edge. Becomes effective only on the next active clock edge. Easier to handle during timing analysis.
• Asynchronous Reset: Independent of the clock. Takes effect immediately, regardless of the clock. Can introduce timing hazards if not managed carefully.

Understanding reset behavior and corresponding timing diagrams is vital to ensure the correct operation of finite state machines and other sequential blocks.

✅ Recommendation: Choose the reset strategy based on design requirements and ensure clear documentation.

Internal clocks are sometimes derived from system clocks using combinational logic. While this might appear to simplify control, it introduces serious challenges:
• Propagation delays in combinational paths can result in glitches or spikes.
• These glitches may inadvertently trigger sequential elements, leading to timing violations or unexpected behavior.

✅ Recommendation: Minimize the use of internally generated clocks. Instead, rely on dedicated clock signals and proper clock management techniques to avoid unpredictable issues.