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                                样例使用说明
                                Sample Description
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功能描述：
定时器1的使能由定时器3控制，当定时器3计数时，LED会常亮，当定时器3发生更新事件时，
更新事件会触发定时器1，定时器1开始计数后，LED会以5Hz的频率进行翻转。

Function descriptions:
The enable of TIM1 is controlled by TIM3. When TIM3 counts, the LED will be 
steady on. The update event generated by TIM3 will triggers TIM1, and when TIM1 
starts counting, the LED is toggled at a frequency of 5Hz
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测试环境：
测试用板：PY32F403_STK
MDK版本： 5.28
IAR版本： 9.20
GCC版本：GNU Arm Embedded Toolchain 10.3-2021.10

Test environment:
Test board: PY32F403_STK
MDK Version: 5.28
IAR Version: 9.20
GCC Version: GNU Arm Embedded Toolchain 10.3-2021.10
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使用步骤：
1. 下载程序并运行；
2. 运行程序，在仿真模式下查看，TIM1先不会计数,当TIM3发生更新事件后，
TIM1开始计数
3. TIM1开始计数后，LED会以5Hz的频率进行翻转

Example execution steps:
1. compile and download the program to MCU and run it;
2. Run the program and check it in debug mode. TIM1 will not count first.
After an update event occurs in TIM3,TIM1 starts counting
3. After TIM1 starts counting, the LED will flip at a frequency of 5Hz
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注意事项：

Notes:

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