ACtE08 · Chapter 8Mock Test 06🏛️ Past Licensure QuestionID: c7c0f6dd
Which of the following statements is INCORRECT for a microprocessor system using I/O-mapped I/O (isolated I/O)?
Which of the following statements is INCORRECT for a microprocessor system using I/O-mapped I/O (isolated I/O)?
Multiple Choice Options
- A✓ Correct Option
I/O address space is greater than memory address space
- B
I/O and memory address spaces are distinct
- C
Entire memory space remains available for system RAM/ROM
- D
Not all data transfer instructions are available for I/O
Detailed Technical Solution & Explanation
In I/O-mapped I/O (Isolated I/O, as implemented in Intel 8085/8086 architectures):
•
Memory and I/O have completely separate address spaces distinguished by control signals (e.g., in 8085).
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The I/O address bus is typically 8-bit (giving only ports) or 16-bit, whereas the memory address bus is 16-bit () to 32/64-bit (). Therefore, the I/O address space is significantly smaller than the memory address space, making the statement 'I/O address space is greater' blatantly incorrect.
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Only dedicated I/O instructions (
IN and OUT) can access I/O ports; general memory instructions (MOV, LDA, arithmetic) cannot directly operate on I/O ports.Option Analysis:
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Option A (I/O address space is greater than memory address space): Correct choice (false statement); I/O address space is far smaller (e.g., 256 ports vs 64 KB memory in 8085).
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Option B (I/O and memory address spaces are distinct): True statement; separated by hardware decoding signals.
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Option C (Entire memory space remains available for system RAM/ROM): True statement; no memory addresses are consumed by I/O devices.
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Option D (Not all data transfer instructions are available for I/O): True statement; restricted strictly to
IN and OUT operations.Reference: Mock Test 06NEC Licensure Syllabus