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                                样例使用说明
                             Sample Description
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功能描述：
此样例演示了切换系统时钟功能。先初始化系统时钟为PLL，HCLK分频为系统时钟一分频，PCLK分频为HCLK一分频。再切换系统时钟为HSI，
LSCLK时钟源为LSI。再切换系统时钟为PLL，LSCLK时钟源为LSI。

Function descriptions:

This example demonstrates the function of switching the system clock. First, initialize the system clock to PLL, 
HCLK division to system clock one division, and PCLK division to HCLK one division. Switch the system clock to HSI again,
The LSCLK clock source is LSI. Switch the system clock to PLL and the LSCLK clock source to LSI.
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测试环境：
测试用板：DPM32M087RBTx_EVB V1.0
MDK版本： 5.28

Test environment:
Test board: DPM32M087RBTx_EVB V1.0
MDK Version: 5.28
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使用步骤：
1. 接上P10上的跳线帽，将串口接到USB。
2. 编译下载程序到MCU，并运行。
3. 可观察到开发板上的LED1每隔1s翻转一次。
4. 串口打印系统源信息。

Example execution steps:
1. Connect the jumper cap on P10 and connect the serial port to USB.
2. Compile and download the program to MCU, and run it.
3. It can be observed that LED1 on the development board flips every 1 second.
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注意事项：
LED引脚如下：
LED1       -> PC10

UART引脚如下：
UART_Tx    -> PA9
UART_Rx    -> PA10

MCO引脚如下：
MCO    -> PA8

Notes:
The LED pins are as follows:
LED1       -> PC10

The UART pins are as follows:
UART_Tx    -> PA9
UART_Rx    -> PA10

The MCO pins are as follows:
MCO    -> PA8
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