Universal shift register — What do you call a shift register that accepts a parallel load and can shift data either left or right?

Introduction:
Many applications require both parallel interfacing and directional shifting for alignment, serialization, or arithmetic. The device that provides all these capabilities is commonly known as a universal shift register.

Given Data / Assumptions:

• Parallel loading needed for fast initialization or bus transfers.
• Ability to shift left or right on command.
• Standard control inputs for mode selection.

Concept / Approach:

A universal shift register supports four primary modes: hold (no change), shift left, shift right, and parallel load. Because it can shift in both directions and accept a parallel word, it is termed a bidirectional universal shift register. Typical IC examples are the 74x194/195 families.

Step-by-Step Solution:

Verification / Alternative check:

Datasheets name these parts “universal” exactly because they combine bidirectional shifting with parallel loading, unlike simpler SIPO or PISO devices that lack at least one capability.

Why Other Options Are Wrong:

• Tri-state: Refers to output enable behavior, not shifting modes.
• End around: Describes feedback to form ring/Johnson counters, not general loading/shifting.
• Conversion: Vague; does not denote register capabilities.
• SIPO/SISO hybrid without parallel load: Lacks the required parallel loading feature.

Common Pitfalls:

• Confusing parallel load with synchronous set/reset; load replaces the entire word.
• Neglecting direction control setup/hold timing before the clock edge.

Final Answer:

bidirectional universal