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STM32F207 EXTI Operation and Clock Confusion

Question asked by hairy.lee on Jan 4, 2016
Latest reply on Jan 9, 2016 by wolff.roger


I was hoping that I might get some clarification regarding the EXTI on the STM32F207. Looking at Fig 4 (STM32F20x block diagram) within the datasheet, it would appear to be APB2; this seems to be further confirmed in section 8.2 of the reference manual.

When HAL_GPIO_Init() is called and the EXTI is configured the __SYSCFG_CLK_ENABLE(); macro is called which sets the SYSCFGEN bit within the RCC_APB2ENR register. To confirm my understanding I called  __SYSCFG_CLK_DISABLE(); before entering a while loop (which just sits waiting for an interrupt from a button press) my expectation was that the interrupt would not kick, but it did and now I’m confused.

My confusion might be fuelled by this being the 1st day back after the holidays, but after trawling through a variety of google searches I couldn’t find anything that explains why this is occurring. If polling the button press I clearly need the GPIOxEN bit set within RCC_AHB1ENR register to detect the state change so am I looking at the wrong clock?