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                                样例使用说明
                             Sample Description
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功能描述：
此样例演示了在EPWM1中基本计数功能，并使能了事件触发(ET)子模块的中断，事件在
TBCTR=TBPRD时生成，同时开启事件分频，每两次TBCTR=TBPRD时会产生一次中断，并在中断中
翻转LED灯。

Function descriptions:
This sample demonstrates the basic counting function in EPWM1, with the Event
Trigger (ET) submodule's interrupt enabled. The event is generated when TBCTR
equals TBPRD. Additionally, event prescaling is activated, producing an
interrupt every two occurrences of TBCTR equaling TBPRD, and the LED is toggled
within the interrupt service routine.

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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. 编译并下载程序；
2. 通过逻辑分析仪捕捉PB2引脚的电平，观察到PB2引脚上电平每2us翻转一次

Example execution steps:
1.Compile and download the program.
2.Use a logic analyzer to capture the signal level on pin PB2. It can be
observed that the signal level on pin PB2 toggles every 2 μs.

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注意事项：
通过USB转TTL模块连接PC与STK板,STK板与USB转TTL模块的连线方式如下；
@PrintfConfigStart
STK板        USB转TTL模块
PA2(TX)  -->  RX
PA3(RX)  -->  TX
GND       -->  GND
UART配置为波特率115200，数据位8，停止位1，校验位None
@PrintfConfigEnd

Notes:
Connect the PC to the STK board through the USB to TTL module, and the connection
method between the STK board and the USB to TTL module is as follows:
@PrintfConfigStart
STK board USB to TTL module
PA2(TX)  -->  RX
PA3(RX)  -->  TX
GND       -->  GND
UART is configured as BaudRate 115200, data bit 8, stop bit 1, and parity None.
@PrintfConfigEnd
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