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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PVD电压检测功能，样例中配置PB07引脚的电压与VREF(1.2v)进行比较，当
PB07引脚的电压高于VREF时,LED灯灭，当低于VREF时，LED灯亮。

Function descriptions:
This sample demonstrates the PVD (Power Voltage Detector) voltage detection 
function. It configures PB07 pin to compare its voltage with VREF (1.2V). 
When the voltage of PB07 exceeds VREF, the LED turns off. When it is lower 
than VREF, the LED lights up.
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测试环境：
测试用板：PY32MD320_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: PY32MD320_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. PB07输入0V时，进入PVD中断，LED灯亮，PB07悬空时（内部上拉相当于接入3.3V）LED灯
灭；
3. 再次输入0V，LED灯亮。

Example execution steps:
1.Compile and download the program to the MCU and run it.
2.When PB07 is set to 0V, it triggers the PVD interrupt and the LED lights up. 
When PB07 is floating (internally pulled up to 3.3V), the LED turns off.
3.Set PB07 to 0V again, and the LED lights up.
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注意事项：
1. 本样例中PB07引脚被配置为上拉，因此PB07悬空时PVDO的状态为0。
2. 低功耗应用中，PVD时钟源应该选择LSC，否则无法正常工作。

Notes:
1. The PB07 pin is configured as pull-up in this sample, so the state of PVDO 
is 0 when PB07 is suspended.
2. In low-power applications, the PVD clock source should be selected as LSC, 
otherwise it will not work properly.
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