Definition – parallel load in a shift register What is meant by a “parallel load” operation for a shift register?

Introduction / Context:
Shift registers support two fundamental ways to enter data: serial and parallel. Parallel load is used whenever an entire word must be captured at once, such as sampling a bus or synchronizing external inputs.

Given Data / Assumptions:

• A generic N-bit shift register with individual flip-flops.
• Control inputs select between shift mode and load mode.
• In load mode, external lines D[N−1:0] present a data word.

Concept / Approach:
Parallel load means that on a single strobe (often a clock edge while a load control is active), every flip-flop captures its corresponding input bit simultaneously. This contrasts with serial loading, which requires N clock pulses to enter N bits.

Step-by-Step Solution:
Assert the parallel load control (e.g., /PL = 0).Present the data word on the parallel inputs.On the qualifying clock or strobe, all flip-flops latch their input bits at the same time, completing the load in one operation.

Verification / Alternative check:
Datasheets for universal shift registers (e.g., 74xx194/195) show mode tables where the “load” mode captures all D inputs concurrently on a clock edge.

Why Other Options Are Wrong:
One-at-a-time or MSB/LSB-only actions describe serial loading or specific preset/clear functions, not parallel load.“Shifted from MSB” is, by definition, serial shifting, not parallel loading.

Common Pitfalls:
Confusing “preset/clear” with “parallel load,” and assuming that a parallel load requires multiple clocks. It is a one-cycle snapshot of the entire word.

Final Answer:
All flip-flops are loaded simultaneously with a data word