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                                样例使用说明
                                Sample Description
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功能描述：
此样例演示了WWDG的提前唤醒中断功能，看门狗计数器向下计数到0x40时产生中断，中断
中喂狗，可以确保看门狗不会复位。

Function descriptions:
This sample demonstrates the early wake-up interrupt function of the WWDG. 
When the watchdog counter counts down to 0x40, an interrupt is generated. 
In the interrupt handler, refresh WWDG counter to ensure that the watchdog 
does not reset the system.
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测试环境：
测试用板：PY32F040_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: PY32F040_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. 编译下载程序并运行；
2. 程序在看门狗提前唤醒中断中喂狗，LED以1hz在闪烁。

Example execution steps:
1.Compile and download the program and run it.
2.Refresh WWDG counter in the watchdog early wake-up interrupt, and the LED
blinks at a frequency of 1Hz.
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注意事项：
如果需要使用按键:
StartKit版本为V2.0以下,需将StartKit.h中的StartKitVersion 2 注释掉，并打开
StartKitVersion 1
StartKit版本为V2.0及以上版本,则无需操作

Notes:
If you need to use buttons:
StartKit version is below V2.0, you need to comment StartKitVersion 2 in
StartKit.h, and open StartKitVersion 1 
StartKit version is V2.0 and above, no operation is required

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