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📝 Right Entry Mode(Calculator Mode) of 8279

📖 From An Introduction To Microprocessor 8085 • 10. Programmable Keyboard and Display Interface: 8279 • 9 questions available

Practice MCQs for Right Entry Mode(Calculator Mode) of 8279. 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. If a microprocessor wants to read counter 1, which combination of control signals must be active according to the 8253 table?

🔹 A. CS=0, RD=0, WR=1, A1=0, A0=1

🔹 B. CS=0, RD=1, WR=0, A1=0, A0=1

🔹 C. CS=1, RD=0, WR=0, A1=0, A0=1

🔹 D. CS=0, RD=0, WR=0, A1=0, A0=1

💡 Difficulty: easy | ✅ Correct: A

Q2. When programming the 8253 to load counter 2 with a count value, which pins must be driven low simultaneously?

🔹 A. CS=0, RD=0, WR=0, A1=0, A0=1

🔹 B. CS=0, RD=0, WR=0, A1=1, A0=1

🔹 C. CS=0, RD=0, WR=0, A1=1, A0=0

🔹 D. CS=0, RD=1, WR=0, A1=1, A0=0

💡 Difficulty: medium | ✅ Correct: C

Q3. If CS is left high while attempting to write a mode word, what is the resulting action of the 8253?

🔹 A. Load the selected counter

🔹 B. Write the mode word to the register

🔹 C. Read the selected counter

🔹 D. No operation (device disabled)

💡 Difficulty: hard | ✅ Correct: A

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🔗 Related Topics

📝 INTEL Programmable Keyboard/Display Interface 8279 📝 Block Diagram of 8279 📝 Functional Description of 8279 📝 Key Board San of 8279 📝 Scanned Keyboard of 8279

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