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📝 Asynchronous Software Approach IC 8251 in 8085A Microprocessor

📖 From An Introduction To Microprocessor 8085 • 14. Serial Communication and Programmable Communication Interface • 15 questions available

Practice MCQs for Asynchronous Software Approach IC 8251 in 8085A Microprocessor. Test your knowledge with carefully crafted questions across easy, medium, and hard difficulty levels.

🔄 Last updated: 2026-07-30

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Q1. What is the maximum number of bytes that the 8257 DMA controller can transfer without CPU intervention?

🔹 A. 8192

🔹 B. 16384

🔹 C. 32768

🔹 D. 65536

💡 Difficulty: easy | ✅ Correct: B

Q2. How does the Address Enable (AEN) pin affect the operation of the 8257 DMA controller when multiple devices share the address bus?

🔹 A. It disables the address bus during DMA

🔹 B. It allows the DMA controller to place an address only when asserted

🔹 C. It forces the CPU to supply the address

🔹 D. It has no effect on bus sharing

💡 Difficulty: medium | ✅ Correct: A

Q3. In a system where Channel 2 of the 8257 is configured for block transfer mode, how does the modulo 128 feature influence successive transfer cycles?

🔹 A. It resets the address after 128 bytes

🔹 B. It masks the high address bits to keep the address within a 128‑byte page

🔹 C. It limits the terminal count to 128 bytes

🔹 D. It has no effect on block transfers

💡 Difficulty: hard | ✅ Correct: D

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🔗 Related Topics

📝 Serial Data Communication IC 8251 in 8085A Microprocessor 📝 Modem IC 8251 in 8085A Microprocessor 📝 Serial Communication Standard IC 8251 in 8085A Microprocessor 📝 Programmable Communication Interface IC 8251 in 8085A Microprocessor 📝 Block Diagram of 8251A in 8085A Microprocessor

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