NIOS II Interrupt Registration

Hello,

My question is with regard to using NIOS II Interrupts on a Cyclone IV E board.

The NIOS II was designed using the QSYS module within quartus and a VIC was added in order to allow for external hardware interrupts. I then register the interrupt in C-code using the enhanced API. The function then returns a success (0 on success) yet the program does not hand over functionality to the ISR.

Here's my registration function:

   int check = alt_ic_isr_register(ENCODER_INPUT_A_IRQ_INTERRUPT_CONTROLLER_ID , // Encoder A ID from System.h
		               ENCODER_INPUT_A_IRQ,                            // Encoder A macro from System.h
		               nios_isr,                                       // Programmer defined Interrupt service routine (seeabove)
		               base,                                           // Optional, unused, only concerned about a single hardware interrupt
		               NULL);                                          // Flag -- Reserved

and my ISR looks like this:

void nios_isr(void* context) {
	count++;
}

Any suggestions? (Note: base is declared as null.)