Question

Which port in 8051 microcontroller requires external pull-up as shown below? 

• A. Port 0
• B. Port 1
• C. Port 2
• D. Port 3

Hint:

Remember that Port 0 requires external pull-up resistors in 8051 microcontrollers.

Answer 1

The Correct Option is A

- Port 0 of the 8051 microcontroller requires external pull-up resistors because it is an open-drain port. 
- Other ports have built-in pull-up resistors. 
Conclusion: The correct answer is option (a).