I am using STM32G491 FDCAN modules 1 and 2 in bare metal. While everything works perfectly on CAN2 the interrupt on CAN1 is constantly disabled. And I do not mean the flags but the actual interrupt does not fire. Each time the interrupt for CAN2 fires, the interrupt from CAN1 is disabled. When I read out the register NVIC->ISER[0] after initialization then I can see bits 6 (EXTI0) and 21 (FDCAN1_IT0) are set. Once FDCAN2 interrupt fires these two bits are reset to 0. I need to enable them again in the ISR of CAN2. How can this happen? How can the interrupt simply be disabled by a different interrupt?
