Question

A periodic interrupt has been programmed to go off every 50ms and is handled by the ISR interrupt_handler(). With a 100 kHz clock, consider the code sequence below that uses the global variable pProcessInterrupt as a flag to tell the main thread to process some data every time the interrupt is triggered. How many times will the main thread read "0" for pProcessInterrupt before it calls process ()? The initial conditions are pProcessInterrupt = 0; Assume that when the interrupt returns, the program is set to execute the while (1) (line 1) statement. Hint: Assume the program has been running for a while, and ignore the time before the first interrupt goes off. // Main thread /Line No./ /01:/while (1) { // 1 cycle to loop /02:/ if (1 == pProcessInterrupt) { // 1 cycle to check the flag /03:/ process(); // 93 cycles to run the processing /04:/ pProcessInterrupt = 0; // 1 cycle to set the flag back to 0 /05:/ } // assume 0 cycles for this line /06:/} // assume 0 cycles for this line // Assume 1 cycle to transition to the interrupt /07:/void interrupt_handler() { /08:/ // interrupt takes 2 cycles /09:/ pProcessInterrupt = 1; /10:/ interruptPending = 0; /11:/} // Assume 1 cycle to transition back to the main program

          A periodic interrupt has been programmed to go off every 50ms and is handled by the ISR interrupt_handler(). With a 100 kHz clock, consider the code sequence below that uses the global variable pProcessInterrupt as a flag to tell the main thread to process some data every time the interrupt is triggered. How many times will the main thread read "0" for *pProcessInterrupt before it calls process ()? The initial conditions are *pProcessInterrupt = 0; Assume that when the interrupt returns, the program is set to execute the while (1) (line 1) statement.
Hint: Assume the program has been running for a while, and ignore the time before the first interrupt goes off.
// Main thread
/*Line No.*/
/*01:*/while (1) { // 1 cycle to loop
/*02:*/ if (1 == *pProcessInterrupt) { // 1 cycle to check the flag
/*03:*/ process(); // 93 cycles to run the processing
/*04:*/ *pProcessInterrupt = 0; // 1 cycle to set the flag back to 0
/*05:*/ } // assume 0 cycles for this line
/*06:*/} // assume 0 cycles for this line
// Assume 1 cycle to transition to the interrupt
/*07:*/void interrupt_handler() {
/*08:*/ // interrupt takes 2 cycles
/*09:*/ *pProcessInterrupt = 1;
/*10:*/ *interruptPending = 0;
/*11:*/} // Assume 1 cycle to transition back to the main program

A periodic interrupt has been programmed to go off every 50ms and is handled by the ISR interrupthandler(). With a 100 kHz clock, consider the code sequence below that uses the global variable pProcessInterrupt as a flag to tell the main thread to process some data every time the interrupt is triggered. How many times will the main thread read "0" for *pProcessInterrupt before it calls process ()? The initial conditions are *pProcessInterrupt = 0; Assume that when the interrupt returns, the program is set to execute the while (1) (line 1) statement.
Hint: Assume the program has been running for a while, and ignore the time before the first interrupt goes off.
// Main thread
/*Line No.*/
/*01:*/while (1) // 1 cycle to loop
/*02:*/ if (1 == *pProcessInterrupt) // 1 cycle to check the flag
/*03:*/ process(); // 93 cycles to run the processing
/*04:*/ *pProcessInterrupt = 0; // 1 cycle to set the flag back to 0
/*05:*/ // assume 0 cycles for this line
/*06:*/ // assume 0 cycles for this line
// Assume 1 cycle to transition to the interrupt
/*07:*/void interrupthandler()
/*08:*/ // interrupt takes 2 cycles
/*09:*/ *pProcessInterrupt = 1;
/*10:*/ *interruptPending = 0;
/*11:*/ // Assume 1 cycle to transition back to the main program

Added by Iker F.

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