Question

The external interrupts of 8051 microcontroller are

• A. \( \text{TRAP and INT1} \)
• B. \( \text{INT2 and INT1} \)
• C. \( \text{INT0 and INT1} \)
• D. \( \text{TRAP and INTR} \)

Hint:

For the 8051 microcontroller, remember its five interrupt sources: two external (\( \overline{\text{INT0}} \), \( \overline{\text{INT1}} \)), two timer overflows (\( \text{TF0} \), \( \text{TF1} \)), and one serial port interrupt (\( \text{RI/TI} \)). These are crucial for embedded systems programming. Also, note that external interrupts can be configured as either edge-triggered or level-triggered.

Answer 1

The Correct Option is C

The 8051 microcontroller has a specific set of interrupt sources, some internal and some external. Interrupts are mechanisms that allow the microcontroller to respond to asynchronous events. The 8051 has five interrupt sources in total:

• Timer 0 overflow interrupt (TF0): Internal interrupt.
• Timer 1 overflow interrupt (TF1): Internal interrupt.
• Serial port interrupt (RI or TI): Internal interrupt.
• External interrupt 0 (INT0): Triggered by a signal on the \( \overline{\text{INT0}} \) pin (P3.2).
• External interrupt 1 (INT1): Triggered by a signal on the \( \overline{\text{INT1}} \) pin (P3.3).

The question specifically asks for the external interrupts of the 8051 microcontroller. Based on the standard 8051 architecture:

• \( \overline{\text{INT0}} \): Connected to pin P3.2
• \( \overline{\text{INT1}} \): Connected to pin P3.3

Let us now evaluate the options:

• (A) \( \text{TRAP and INT1} \): TRAP is an interrupt in microprocessors like the 8085, not in 8051. INT1 is valid.
• (B) \( \text{INT2 and INT1} \): INT2 is not present in the standard 8051; it may appear in some variants.
• (C) \( \text{INT0 and INT1} \): Both are valid external interrupts for the standard 8051 microcontroller.
• (D) \( \text{TRAP and INTR} \): These belong to other microprocessors like 8085 or x86, not the 8051.

Hence, the correct external interrupts of the 8051 microcontroller are \( \text{INT0} \) and \( \text{INT1} \).