Digital clock design using synchronous counters In the digital clock project, the 1 pulse-per-second (1 pps) signal is used as the common synchronous clock for all counter stages, which are designed to be synchronous cascaded stages.

Introduction / Context: A digital clock typically counts seconds, minutes, and hours using BCD counters. Using a single, clean time base ensures that all digits change coherently and avoids ripple delays or glitches associated with asynchronous designs.

Given Data / Assumptions:

• The clock provides a 1 pps reference (already debounced and stable).
• All counting stages (seconds, minutes, hours) share this same clock edge.
• Cascading between digits is synchronous using enable/carry signals.

Concept / Approach: Synchronous cascading means every flip-flop in all stages is clocked by the same 1 pps signal. Inter-stage connections use enable or ripple-carry-out signals to control when higher-order digits increment, maintaining precise timing and eliminating ripple skew.

Step-by-Step Solution:

Verification / Alternative check: Simulate 0–59 seconds and 0–59 minutes to confirm orderly rollover at 59 → 00 with an increment of the next stage.

Why Other Options Are Wrong: “advanced BCD counters” describes a type, not the cascade method. “MOD-6 counters” applies only to some digits, not all. “1 pulse per second” restates the clock source, not the cascade property.

Common Pitfalls: Mixing asynchronous ripple counters; forgetting synchronous enables; mishandling the 59→00 rollover.

Final Answer: synchronous cascaded