Counters — Meaning of a Parallel Load Operation In synchronous digital design, what is meant by a parallel load of a counter or register? Choose the best description that captures how data is applied and when it is captured by the flip-flops (FFs).

Introduction / Context:
A fundamental capability of synchronous counters and registers is the ability to capture a multi-bit value in one operation. This is commonly called a parallel load. Understanding how and when a parallel load occurs helps students correctly wire control signals such as load, reset, and enable, and to predict timing behavior in finite-state machines and data paths.

Given Data / Assumptions:

• The device is a synchronous counter or register built from edge-triggered flip-flops.
• The device provides dedicated parallel data inputs (e.g., D3..D0) and a load control input (e.g., LD or PL).
• The system uses a single system clock to coordinate state changes.

Concept / Approach:
Parallel load means the multi-bit value present on the external data inputs is transferred into all internal flip-flops simultaneously at the designated clocking event when the load control is asserted. This is different from serial loading (one bit per clock) and from asynchronous preset/clear (which forces 1s or 0s independent of the clock).

Step-by-Step Solution:
Identify control: the load input (active-HIGH or active-LOW) enables the parallel capture.Clocking: on the active clock edge, with load asserted, each FF captures its corresponding D input bit.Result: the N-bit register changes all bits concurrently to match the applied N-bit word.Contrast: with load deasserted, the device either counts (for counters) or holds (for registers) per its normal function.

Verification / Alternative check:
Datasheets for common counters (e.g., 74161/74163 synchronous counters) show a parallel load input (PL). When PL is active, Q takes D on the next clock; when PL is inactive, the device counts or holds according to enable signals. Simulation confirms that all bits update together at the clock edge.

Why Other Options Are Wrong:

• Each flip-flop loaded on separate clocks: That describes a sequential or staged load, not parallel loading.
• The counter is cleared: That is reset, not load.
• All FFs are preset asynchronously: Asynchronous preset ignores the clock and forces 1s, not arbitrary data words.

Common Pitfalls:
Confusing “preset/clear” with “load,” and assuming load acts immediately without a clock; in synchronous parts, loading occurs at the clock edge when the load control is asserted.

Final Answer:
All flip-flops are simultaneously loaded from their parallel data inputs on a single active clock edge.