1、功能说明
    1、TIM2 利用更新中断，产生定时翻转IO
2、使用环境
    软件开发环境：  KEIL MDK-ARM 5.34.0.0
    硬件环境：      基于N32A455VEL7_EVB v1.0.0开发
3、使用说明
    系统配置；
        1、时钟源：
            HSE=8M,PLL=144M,AHB=144M,APB1=36M,APB2=72M,TIM2 CLK=72M
        2、中断：
            TIM2 更新中断打开，抢断优先级0，子优先级1
        3、端口配置：
            PC6选择为IO输出
            PC7选择为IO输出
            PC8选择为IO输出
            PC9选择为IO输出
        4、TIM：
            TIM2使能周期中断
    使用方法：
        1、编译后打开调试模式，用示波器或者逻辑分析仪观察PC6的波形
        2、程序运行后，TIM2的周期中断来临翻转PC6电平
4、注意事项
    无


1. Function description
     1. TIM2 uses update interrupt to generate timing flip IO
2. Use environment
     Software development environment: KEIL MDK-ARM 5.34.0.0
     Hardware Environment: Developed based on N32A455VEL7_EVB v1.0.0
3. Instructions for use
     System Configuration;
         1. Clock source:
             HSE=8M,PLL=144M,AHB=144M,APB1=36M,APB2=72M,TIM2 CLK=72M
         2. Interrupt:
             TIM2 update interrupt on, steal priority 0, sub-priority 1
         3. Port configuration:
             PC6 is selected as IO output
             PC7 is selected as IO output
             PC8 is selected as IO output
             PC9 is selected as IO output
         4. TIM:
             TIM2 enables periodic interrupts
     Instructions:
         1. Open the debug mode after compiling, and observe the waveform of PC6 with an oscilloscope or logic analyzer
         2. After the program runs, the cycle of TIM2 is interrupted and the level of PC6 is flipped
4. Matters needing attention
     none