Keil debugger(ST-Link Debugger) question

Hello,

I wrote an application in which I used an STM32F446 controller(from an STM-32 nucleo board) to configure an external interrupt using a push button.

This is my configuration:

• enabled EXTI0 line and I'm using my push button connected to PA0 to generate falling edge interrupts
• I have implemented the 'EXTI0_IRQHandler' function and confirmed that the code goes there and the interrupt gets processed properly.

However I still have one thing about the debugger which bugs me :). I have put few two breakpoints in the endless while(1) loop to see the flow of the code like this: one on line 47(int a = 1) one on line 49(in c = 3). Then one breakpoint in the ISR to make sure the code goes there when I press the button. If I cycle through the breakpoints by 'run'(f5) then everything works fine. However if I just step through the code in the while loop(by pressing f10) and then I press the button to trigger the falling edge interrupt I would expect the code to go to line 56(beginning of the ISR). However that does not happen. The interrupt request gets processed, the isr gets pendet however the code keeps cycling through the while loop instead of going to the ISR when I press f10. Why is this happening? Below is my code:

#include "stm32f446xx.h"
#include "Board_LED.h"
#include "Board_Buttons.h"
 
// PA1(led) - output, push pull (SWITCH FROM BELOW(PA0) to PA1)
void leds_initialize()
{
 RCC->AHB1ENR |= (1ul << 0); /* Enable GPIOA clock */
	// configure pa1(the led)
 GPIOA->MODER |= ( 1 << 2 ); 
 GPIOA->MODER &= ~( 1 << 3 ); 
	GPIOA->OTYPER &= ~( 1 << 1 ); 
	// initially led is off
	GPIOA->ODR &= ~(1 << 1);
}
 
// button(pa0)
void buttons_initialize()
{
	// configure PA0(the button) - input/pull down
	GPIOA->MODER &= ~( 1 << 0 );
	GPIOA->MODER &= ~( 1 << 0 );
	
	
	GPIOA->OTYPER &= ~( 1 << 0 );
	
	GPIOA->PUPDR &= ~( 1 << 0 );
	GPIOA->PUPDR |= ( 1 << 1 );
	
	// configure the interrupt part
	SYSCFG->EXTICR[0] = SYSCFG_EXTICR1_EXTI0_PA; // enable PA0 as EXTI0(macro = 0x0000U)
	EXTI->IMR |= ( 1 << 0 ); // interrupt request from line 0 is NOT MASKED
	EXTI->RTSR &= ~( 1 << 0); // rising trigger disabled for external interrupt input line 0
	EXTI->FTSR |= ( 1 << 0 ); // falling trigger enabled for external interrupt input line 0
	
	/* ENABLE THE CORRESPONDING NVIC LINE WHERE EXTI0 LINE IS CONNECTED */
 NVIC->ISER[0] |= ( 1 << EXTI0_IRQn );
}
 
int main(void)
{
 leds_initialize();
	buttons_initialize();
		
	while(1)
	{
	 int a = 1;
	 int b = 2;
	 int c = 3;
	}
	
	return 0;
}
 
#if 1
void EXTI0_IRQHandler(void)
{
	// Check if the pending bit for exti0 is really set before processing the interrupt 
 if( (EXTI->PR) & 0x01 )
	{
	 EXTI->PR |= 1; // clear the bit
		GPIOA->ODR ^= ( 1 << 1 ); // toggle the LED
	}
	 
}

Thank you for reading!