Synchronous vs. asynchronous counters — eliminating ripple delay Why do synchronous counters avoid the cumulative propagation delays seen in asynchronous (ripple) counters?

Introduction / Context:
Asynchronous counters propagate state changes from one flip-flop to the next, leading to cumulative ripple delays and temporary incorrect outputs. Synchronous counters are designed to eliminate this behavior so that all bits update together, a crucial advantage in high-speed digital systems.

Given Data / Assumptions:

• Synchronous counter implemented with edge-triggered flip-flops.
• Common system clock distributed to all stages.
• Proper gating logic derives each flip-flop’s next state from the present state.

Concept / Approach:
In synchronous designs, every flip-flop samples its input on the same clock edge. The combinational logic feeding each stage ensures that the correct next value is present at the sampling instant. Because no stage waits for another to toggle first, all outputs change simultaneously, eliminating ripple-through delays at the word output.

Step-by-Step Reasoning:

Verification / Alternative check:
Observe waveforms: in a synchronous counter, all Q outputs transition at the same edge. In a ripple counter, higher-order bits lag lower-order ones by multiple propagation delays, readily visible on a scope as skewed edges and intermediate codes.

Why Other Options Are Wrong:

• First/last stage only or last stage only: still serializes updates and would not prevent ripple behavior.
• No clock used: counters by definition advance with a clock.
• “Faster process”: technology helps but does not fundamentally remove ripple; architecture does.

Common Pitfalls:

• Assuming synchronous eliminates all delay; it eliminates ripple error at the word output, but setup/hold and logic delays still must meet timing.

Final Answer:
input clock pulses are applied simultaneously to each stage