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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lpsleep模式下，GPIO外部中断唤醒功能。

Function descriptions:
This sample demonstrates the GPIO external interrupt wake-up feature in lpsleep mode.
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测试环境：
测试用板：PY32F420_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: PY32F420_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. 编译下载程序到MCU，并运行；
2. LED灯亮，按下按键，LED灯灭，进入lpsleep模式；
3. 在PA06上产生一个下降沿，程序退出lpsleep模式；
4. LED以500ms的间隔进行翻转。

Example execution steps:
1. Compile and download the program to the MCU and run it;
2. The LED will be on initially. Press the button, and the LED will turn off, 
entering lpsleep mode;
3. Generate a falling edge on PA06, and the program will exit lpsleep mode;
4. The LED will toggle at intervals of 500ms.
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注意事项：
1，演示此样例功能时需要断开swd连接线并重新上电，因为默认情况下，仿真器会把
DBGMCU_CR1.DBG_STDBY置位。
2，注意关闭systick中断，防止该中断唤醒MCU。

Notes:
1.To demonstrate this sample function, it is necessary to disconnect the SWD
cable and power it back on, as by default, the emulator will reset the
DBGMCU_CR1.DBG_STDBY position.
2.Pay attention to turning off the systick interrupt to prevent it from waking
up the MCU.
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