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📝 Serial Data Communication IC 8251 in 8085A Microprocessor

📖 From An Introduction To Microprocessor 8085 • 14. Serial Communication and Programmable Communication Interface • 12 questions available

Practice MCQs for Serial Data Communication 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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📝 Sample Questions

Q1. What is the maximum number of bytes that a single DMA transfer can move without CPU intervention?

🔹 A. 8192 bytes

🔹 B. 16384 bytes

🔹 C. 32768 bytes

🔹 D. 4096 bytes

💡 Difficulty: easy | ✅ Correct: B

Q2. How does the HRQ (HOLD Request) signal interact with the HLDA (HOLD Acknowledge) line during a DMA cycle?

🔹 A. HRQ is asserted by the CPU and HLDA is ignored

🔹 B. HRQ is generated by the DMA controller and HLDA is asserted by the CPU to pause it

🔹 C. HRQ is generated by the DMA controller and HLDA is asserted by the CPU to grant bus control

🔹 D. HRQ and HLDA are unrelated signals

💡 Difficulty: medium | ✅ Correct: C

Q3. Why does the Mode Set Register need to be programmed before starting a DMA transfer on a channel?

🔹 A. It sets the CPU clock speed

🔹 B. It defines transfer type, address increment, and auto‑initialization

🔹 C. It controls the power supply to the DMA controller

🔹 D. It selects which IRQ line to use

💡 Difficulty: hard | ✅ Correct: B

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🔗 Related Topics

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

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