Interrupts in 8051 Microcontroller

The 8051 microcontroller has five interrupt sources:

1. External interrupt 0 (INT0): This interrupt is triggered by a falling edge on the INT0 pin (P3.2) or by a low level on the pin, depending on the configuration. It is used for external events that require immediate attention, such as button presses or other input signals.

2. External interrupt 1 (INT1): This interrupt is triggered by a falling edge on the INT1 pin (P3.3) or by a low level on the pin, depending on the configuration. It is used for external events that require immediate attention, such as button presses or other input signals.

3. Timer 0 interrupt: This interrupt is triggered when the Timer 0 register overflows. It is used for timing events or for generating periodic interrupts.

4. Timer 1 interrupt: This interrupt is triggered when the Timer 1 register overflows. It is used for timing events or for generating periodic interrupts.

5. Serial port interrupt: This interrupt is triggered when a byte is received or transmitted on the serial port. It is used for serial communication events.

To use interrupts in the 8051 microcontroller, you need to do the following steps:

1. Configure the interrupt source: You need to configure the interrupt source by setting the appropriate bits in the interrupt enable register (IE). For example, to enable external interrupt 0, you need to set the bit IE.0.

2. Write the interrupt service routine: You need to write the interrupt service routine (ISR) that will be executed when the interrupt occurs. The ISR is a function that performs the required task when the interrupt occurs. The ISR should end with the RET instruction to return control to the main program.

3. Enable interrupts: You need to enable interrupts by setting the EA bit in the interrupt enable register (IE). This allows the microcontroller to respond to interrupts.

Here's an example code snippet that shows how to use interrupts in the 8051 microcontroller:

#include <8051.h>

void external_interrupt_0_isr() __interrupt(0) {
  // Perform the required task
}

void main() {
  // Configure external interrupt 0
  IT0 = 1;    // Interrupt on falling edge
  EX0 = 1;    // Enable external interrupt 0

  // Enable interrupts
  EA = 1;

  while (1) {
    // Perform the main program tasks
  }
}

In this example, the external interrupt 0 is configured to trigger on the falling edge of the signal on the INT0 pin. The external_interrupt_0_isr() function is the ISR that will be executed when the interrupt occurs. The __interrupt(0) keyword specifies that this function is the ISR for external interrupt 0. The main program continuously runs in the while loop, while the microcontroller waits for the interrupt to occur.