Digital clock design (HDL): purpose of the frequency prescaler In a 12-hour digital clock project, identify the main purpose of the prescaler (frequency divider) used ahead of the seconds counter.

Introduction / Context:
Digital clocks require an accurate 1 pulse per second (1 pps) tick to advance seconds. Real-world reference sources (mains 60 Hz or crystals like 32.768 kHz) must be divided down to 1 Hz. The prescaler (frequency divider) performs this task, delivering a clean timing reference to the seconds counter.

Given Data / Assumptions:

• Clock reference might be 60 Hz (or 50 Hz, or a crystal frequency).
• Seconds counters advance on a 1 Hz enable pulse.
• We are focusing on the prescaler function, not on display range-limiting logic.

Concept / Approach:
The prescaler divides a higher-frequency reference to the required base timing. For a 60 Hz mains reference, dividing by 60 produces 1 Hz (1 pps). This pulse then clocks the seconds unit counter reliably.

Step-by-Step Solution:

Verification / Alternative check:
Designs using crystals (e.g., 32.768 kHz) similarly divide by powers of 2 to reach 1 Hz; concept is identical.

Why Other Options Are Wrong:

• A: The “basic frequency” is known; prescaler divides it, not finds it.
• C: Rollover logic limits 12:59:59, not the prescaler.
• D: BCD value ranges are enforced by counter modulus and decoding, not the prescaler.

Common Pitfalls:
Mixing up prescaler duties with display decoding or hour/minute rollover logic.

Final Answer:
transform a 60 pps input to a 1 pps timing signal.