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📝 Initialization of 8251A in Synchronous Mode in 8085A Microprocessor

📖 From An Introduction To Microprocessor 8085 • 14. Serial Communication and Programmable Communication Interface • 17 questions available

Practice MCQs for Initialization of 8251A in Synchronous Mode in 8085A Microprocessor. Test your knowledge with carefully crafted questions across easy, medium, and hard difficulty levels.

🔄 Last updated: 2026-07-30

4
Easy Questions
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Medium Questions
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Hard Questions

📝 Sample Questions

Q1. What is the default state of the Synchronous Mode Enable (SME) bit in the 8251A Mode Register after a power‑on reset?

🔹 A. 0 (disabled)
🔹 B. 1 (enabled)
🔹 C. Undefined until programmed
🔹 D. Depends on external pins

💡 Difficulty: easy | ✅ Correct: B

Q2. Why must the Baud Rate Generator (BRG) be disabled before setting the synchronous clock divisor?

🔹 A. Disabling prevents spurious clock edges that could corrupt the divisor latch
🔹 B. The BRG shares the same I/O pins as the divisor, causing contention
🔹 C. The BRG must be idle to allow the CPU to read back the divisor value
🔹 D. The BRG influences only asynchronous mode, not synchronous mode

💡 Difficulty: medium | ✅ Correct: B

Q3. A designer connects the 8251A to a peripheral that supplies a 2 MHz external clock. Which register must be programmed to match this external rate, and what value should be used?

🔹 A. Mode Register, set SME=1 and select divisor 0
🔹 B. Command Register, set synchronous mode and divisor 3
🔹 C. BRG Register, load divisor value 1
🔹 D. Status Register, clear error flags

💡 Difficulty: hard | ✅ Correct: A

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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📝 Asynchronous Software Approach IC 8251 in 8085A Microprocessor📝 Programmable Communication Interface IC 8251 in 8085A Microprocessor
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