STM32抢占优先级与从优先级

NVIC_IRQChannelPreemptionPriority：先占优先级 NVIC_IRQChannelSubPriority：从优先级 高抢占优先级中断可以打断低抢占优先级的中断，即可中断嵌套。抢占优先级号码越小优先级越高当抢占优先级号码相同时，从优先级号码起作用。同抢占优先级下的中断是不能进行嵌套的，只能根据从优先级的号码进行排队，从优先级号码即为排队号码，号码越低越靠前。 如买火车票一样，系统中设置学生、军人的优先级（抢占优先级）高于普通群众，学生、军人可以抢占系统通道，得到优先买票的权力，但学生、军人之间是不能进行抢占的，只能根据排队（从优先级）来决定谁可以先买到票。 先用函数NVIC_PriorityGroupConfig(NVIC_PriorityGroup_x)决定有几个先占优先级和从优先级。NVIC_PriorityGroup_x可取如下： NVIC_PriorityGroup_0 => 选择第0组 NVIC_PriorityGroup_1 => 选择第1组 NVIC_PriorityGroup_2 => 选择第2组 NVIC_PriorityGroup_3 => 选择第3组 NVIC_PriorityGroup_4 => 选择第4组 举例： NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1)；//配置为1组。 NVIC_InitStructure.NVIC_IRQChannel = EXTI0_IRQChannel; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; // 指定抢占式优先级别0，可取0-1 NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE；//使能中断 NVIC_Init(&NVIC_InitStructure); NVIC_InitStructure.NVIC_IRQChannel = SPI1_IRQChannel; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1; // 指定抢占式优先级别1，可取0-1 NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; // 指定从优先级别0，可取0-7 NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQChannel; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1; NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1; // 指定从优先级别1，可取0-7 NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); EXTI0_IRQChannel 抢占优先级比SPI1_IRQChannel、USART1_IRQChannel高，所以EXTI0_IRQChannel中断可以打断正在执行的SPI1_IRQChannel/USART1_IRQChannel中断，实现中断嵌套。 SPI1_IRQChannel、USART1_IRQChannel抢占优先级相等，不能相互打断，即在执行SPI1_IRQChannel/USART1_IRQChannel中断时USART1_IRQChannel/SPI1_IRQChannel中断无法打断。同时产生SPI1_IRQChannel、USART1_IRQChannel中断时，要根据从优先级进行排队，SPI1_IRQChannel从优先级比较高，所以先执行SPI1_IRQChannel中断。