关于LM4F232例程

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楼主

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楼主 | 2020-12-3 09:37 | 只看该作者回帖奖励

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lm, pi, IO, gp, GPIO

以下是网上看到的例程：
没能理解，求解。

int
main(void)
{
volatile unsigned long ulLoop;
//
// Enable the GPIO port that is used for the on-board LED.
//
SYSCTL_RCGC2_R = SYSCTL_RCGC2_GPIOG;
//
// Do a dummy read to insert a few cycles after enabling the peripheral.
//
ulLoop = SYSCTL_RCGC2_R;
//
// Enable the GPIO pin for the LED (PG2).  Set the direction as output, and
// enable the GPIO pin for digital function.
//
GPIO_PORTG_DIR_R = 0x04;
GPIO_PORTG_DEN_R = 0x04;
//
// Loop forever.
//
while(1)
{
      //
      // Turn on the LED.
      //
      GPIO_PORTG_DATA_R |= 0x04;
      //
      // Delay for a bit.
      //
   for(ulLoop = 0; ulLoop < 20; ulLoop++)
   {
   }
      //
      // Turn off the LED.
      //
      GPIO_PORTG_DATA_R &= ~(0x04);
      //
      // Delay for a bit.
      //
      for(ulLoop = 0; ulLoop < 20; ulLoop++)
      {
      }
}
}

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