Microcomputer buses and directionality: Identify which bus in a typical microcomputer system is inherently unidirectional.

Introduction / Context:
Digital systems use several buses to interconnect the CPU, memory, and peripherals. Understanding directionality helps with timing analysis, tri-state design, and bus arbitration. This item focuses on which bus is unidirectional by design.

Given Data / Assumptions:

• Address bus carries memory or I/O addresses from master (often the CPU) to slaves.
• Data bus transfers read or write data, typically bidirectional.
• Control bus carries various signals (read/write, clock, interrupt lines), some driven by CPU, others by peripherals.

Concept / Approach:
The address bus identifies the target location and flows outward from the address source to all addressed devices. Data movement, however, goes in either direction depending on read or write cycles, and control lines vary by role.

Step-by-Step Solution:

Verification / Alternative check:
Textbook bus diagrams consistently show address lines as outputs from the processor toward the system; data lines are shown with bidirectional arrows.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming tri-state implies bidirectionality for all buses; conflating bus masters with signal direction.

Final Answer:
address bus