ACtE04 · Chapter 4Computer Organization & Embedded Systems🏛️ Past Licensure QuestionID: 9fb91c5e
In a unified memory-mapped I/O scheme, which of the following statements correctly describes system architecture?
In a unified memory-mapped I/O scheme, which of the following statements correctly describes system architecture?
Multiple Choice Options
- A✓ Correct Option
I/O devices and system memory share the exact same contiguous address space and control lines
- B
Memory addresses and I/O addresses are physically isolated into separate address spaces
- C
The CPU cannot read data from I/O ports
- D
Dedicated IN and OUT assembly instructions are strictly required
Detailed Technical Solution & Explanation
In memory-mapped I/O, peripheral I/O port registers are assigned addresses within the single unified system memory address space. The CPU uses identical memory read/write instructions (MOV, LDA, STA) and identical bus control lines (MEMR, MEMW) to communicate with both RAM and I/O devices.
Option Analysis:
•
Option A (Share the exact same address space and control lines): Correct; fundamental definition of memory-mapped I/O.
•
Option B (Isolated separate address spaces): Describes Isolated I/O (Port-mapped I/O).
•
Option C (CPU cannot read I/O): False; reads via standard memory load instructions.
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Option D (IN/OUT instructions required): False; IN/OUT are only used in isolated I/O.
Reference: Demo2 · Set 2NEC Licensure Syllabus