Introduction / Context:
Asynchronous (ripple) counters toggle stages sequentially, while synchronous counters clock all stages simultaneously with added combinational logic to determine state transitions. The trade-off is classic: less logic vs. better timing performance.
Given Data / Assumptions:
- Asynchronous counters use minimal gating; propagation ripples through flip-flops.
- Synchronous counters add gating to derive each next state in parallel.
- Target frequency and timing closure influence architecture choice.
Concept / Approach:
Synchronous counters remove ripple delay, enabling higher speeds and predictable timing at the cost of additional gates (look-ahead or decoding logic). Therefore, they generally require more circuitry than ripple counters, which are simpler but slower due to cumulative propagation delay and potential glitches at intermediate counts.
Step-by-Step Solution:
Contrast architectures: ripple (serial toggling) vs. synchronous (parallel update).Identify added logic: synchronous uses gating to compute toggles for each stage.Conclude: more logic resources are typical in synchronous designs.Benefit: improved maximum clock frequency and timing predictability.
Verification / Alternative check:
Synthesis reports show higher LUT/gate count for synchronous implementations compared to ripple equivalents of the same width.
Why Other Options Are Wrong:
Incorrect: Undercuts the well-known trade-off.Frequency/Gray-specific options: The complexity difference holds broadly, not only under special conditions.
Common Pitfalls:
Ignoring that FPGA vendors may offer dedicated carry chains that blur resource differences but not the conceptual trade-off.Confusing “more circuitry” with “less efficient”; it is usually necessary for speed.
Final Answer:
Correct
Discussion & Comments