Q3Microprocessor
Question
Q.3. List the 8051 interrupts with its priority.
Answer
The 8051 has 5 interrupt sources with default priority order (highest to lowest): External Interrupt 0 (INT0), Timer 0 overflow (TF0), External Interrupt 1 (INT1), Timer 1 overflow (TF1), and Serial Port interrupt (RI/TI) — all can be reprioritized into two levels using the IP register.
The 8051 microcontroller has five interrupt sources: External Interrupt 0 (INT0, pin P3.2), Timer 0 overflow interrupt (TF0), External Interrupt 1 (INT1, pin P3.3), Timer 1 overflow interrupt (TF1), and Serial Port interrupt (triggered by either RI, receive interrupt, or TI, transmit interrupt). The default priority order (in case of simultaneous interrupt requests at the same priority level) from highest to lowest is: External Interrupt 0, Timer 0, External Interrupt 1, Timer 1, and Serial Port interrupt — this fixed polling sequence is used only to resolve ties among interrupts of equal (default, low) priority. All five interrupt sources can additionally be individually assigned to either a high or low priority level using the Interrupt Priority (IP) special function register, allowing any interrupt to preempt a lower-priority interrupt currently being serviced, overriding the default polling-sequence tie-break for interrupts explicitly set to different priority levels.