GUIDED BY PROFFESOR NILESH DESAI GROUP NO:-8 CHANDRASHIKHA SINGH( ) KURUP SHUBHAM VALSALAN( ) SAURAV SHUBHAM( )

 In system programming an interrupt is a signal to the processor emitted by hardware or software indicating an event that needs immediate attention.  An interrupt alerts the processor to a high-priority condition requiring the interruption of the current code the processor is executing.  The processor responds by suspending its current activities, saving its state, and executing a function called an interrupt service routine, ISR to deal with the event. This interruption is temporary, and, after the interrupt handler finishes, the processor resumes normal activities.  There are two types of interrupts: hardware interrupts and software interrupts

 Hardware interrupts are used by devices to communicate that they require attention from the operating system Internally, hardware interrupts are implemented using electronic signal.  For example, pressing a key on the keyboard or moving the mouse triggers hardware interrupts that cause the processor to read the keystroke or mouse position.  Unlike the software type (described below), hardware interrupts are asynchronous and can occur in the middle of instruction execution, requiring additional care in programming.  The act of initiating a hardware interrupt is referred to as an interrupt request (IRQ)

 A software interrupt is caused either by an exceptional condition in the processor itself, or a special instruction in the instruction set which causes an interrupt when it is executed.  For example, if the processor's arithmetic logic unit is commanded to divide a number by zero, this impossible demand will perhaps causing the computer to abandon the calculation or display an error message.

 The task is to write a C program, utilizing the external interrupt of the ATMega8515, that when download to the ATMega8515 in the figure below perform one (1) of two (2) operations. On start-up OPERATION 1 is is executed and continue indefinitely. If the push-button switch is pressed OPERATION 1 is paused and OPERATION 2 is carried out after which OPERATION 1 is resumed. OPERATION 1 - A roll action is perform using the LEDs. The first LED is lit and roll down to the last LED then back to the first LED. This operation is done continuous.

#include #define F_CPU UL #include #define DataPort PORTC // Using PortC as our Dataport #define DataDDR DDRC //Interrupt Service Routine for INT0 ISR(INT0_vect) { unsigned char i, temp; _delay_ms(500); // Software debouncing control temp = DataPort; // Save current value on DataPort

 for(i = 0; i<5; i++)  { DataPort = 0x00; _delay_ms(500);  // Wait 5 seconds DataPort = 0xFF; _delay_ms(500); // Wait 5 seconds }  DataPort = temp; //Restore old value to DataPort }  int main(void)  { DDRD = 1<<PD2; // Set PD2 as input (Using for interupt INT0)  PORTD = 1<<PD2; // Enable PD2 pull-up resistor DataDDR = 0xFF; // Configure Dataport as output DataPort = 0x01; // Initialise Dataport to 1 GICR = 1<<INT0; // Enable INT0 MCUCR = 1<<ISC01 | 1<<ISC00; // Trigger INT0 on rising edge sei(); //Enable Global Interrupt

 while(1) { if(DataPort >= 0x80) DataPort = 1; else DataPort =DataPort << 1  ; // Shift to the left delay_ms(500); // Wait 5 seconds } }