With IOTester it is very easy to use interrupt service functions. For instance to service interrupt from an external keyboard-controller or touch-screen-controller device, or from internal IOTester devices.
The interrupt function can be debugged with PC tools as usual.

The program example configures then internal IOTester-USB timer device and interrupt controller device so periodic interrupts are generated. Timer interrupt from IOTester is serviced by an application specific interrupt function on the PC.

#include <iotester.h> // Define IOTester functions and symbolic names for internal registers
#include <stdio.h>    // printf

unsigned int intrcnt;

// Timer interrupt function. 
// The function is called periodically via IOT_TIMER generated interrupts
void timerint_func(void)
   {
   // Service interrupt
   intrcnt++;  // Here we just count number of interrupt events
   // IOTester automatically do End-Of-Interrupt (EOI) handling for internal sources.
   // so no special actions needed here
   }

int main(void)
   {
   unsigned int old_intrcnt = 0;
   intrcnt = 0;

   // Init IOTESTER driver, search for any IOTester-USB connected to the PC
   if (iot_init(0))
      return 1; // Could not connect

   // IOTester connection OK
   iot_wr(IOT_PIN_MODE_REG, 0); // All pins is I/O pins (= hardware reset default)

   //*** Init interrupt system ***

   // Assign our interrupt funcion to the IOTester timer vector 
   iot_set_callback(IOTV_TIMER, &timerint_func);
 
   // Configure IOTester timer for: 20*10ms = 0.2 sec, periodic interrupt (started at once)
   iot_wr(IOT_TIMER_CTRL, IOT_TIMER_PERIODIC | 20);
 
   // Configure IOTester interrupt controller. 
   // Enable timer terminal count to generate interrupt on PC
   iot_wr(IOT_INTENA_SET, IOTIE_GLOBAL | IOTIE_TIMER);

   //*** The interrupt system is now running ***

   // Monitor interrupt generation from the "embedded target" system
   printf("\n Test IOTester Timer interrupt (Console should show count down)\n");

   // Let the timer interrupt hardware generate 100 timer ticks
   while(intrcnt < 100) 
      {
      // Monitor timer count down and report number of interrupt events 
      printf("\r%u %u", iot_rd(IOT_TIMER), old_intrcnt );
      if (intrcnt != old_intrcnt)
          {
          // Next line
          old_intrcnt = intrcnt;
          printf("\n"); 
          }
      }

   // Disable all IOTester timer and interrupt activity and disconnect.
   // This is actually not nessesary here, but just to illustrate how close down is done "the pretty way"
   iot_wr(IOT_INTENA_CLR, ~IOTIE_TIMER); // Disable timer generated interrupt
   iot_wr(IOT_TIMER_CTRL, 0);            // Disable timer counting
   iot_set_callback(IOTV_TIMER, 0);    // Remove interupt vector hook

   iot_exit();                         // Disconnect IOTester
   return 0;
   }

Links to:
IOTester tool description
Example 1: Start using IOTester I/O port pins - "Single chip mode"
Example 2: Enabling the External bus
Example 3: Using Internal Devices and External bus.
Example 4: Using Target Interrupt.
Example 5: Writing portable I/O driver source code with <iohw.h>
Example 6: <iohw.h> implementation methods and definition of I/O registers
Example 7: Swapping source code between PC and target platforms