text: 
  /******************************************************************************
   * @file     main.c
   * @version  V2.00
   * $Revision: 3 $
   * $Date: 15/04/15 5:29p $
   * @brief    Demonstrate how ACMP works with internal band-gap voltage.
   * @note
   * Copyright (C) 2014 Nuvoton Technology Corp. All rights reserved.
  *****************************************************************************/
  #include <stdio.h>
  #include "NUC100Series.h"
  
  #define PLLCON_SETTING      CLK_PLLCON_50MHz_HXT
  #define PLL_CLOCK           50000000
  
  
  /* Function prototype declaration */
  void SYS_Init(void);
  void UART_Init(void);
  
  int32_t main(void)
  {
      /* Unlock protected registers */
      SYS_UnlockReg();
  
      /* Init System, peripheral clock and multi-function I/O */
      SYS_Init();
  
      /* Lock protected registers */
      SYS_LockReg();
  
      /* Init UART for print message */
      UART_Init();
  
      printf("\n\n");
      printf("+---------------------------------------+\n");
      printf("|        NUC100 ACMP Sample Code        |\n");
      printf("+---------------------------------------+\n");
  
      printf("\nThis sample code demonstrates ACMP0 function. Using ACMP0_P (PC.6) as ACMP0\n");
      printf("positive input and using internal band-gap voltage as the negative input\n");
      printf("The compare result reflects on ACMP0_O (PB.12)\n");
  
      /* Configure ACMP0. Enable ACMP0, enable interrupt and select internal reference voltage as negative input. */
      ACMP->CMPCR[0] = ACMP_CMPCR_CMPEN_Msk | ACMP_CMPCR_CMPIE_Msk | ACMP_CMPCR_CMPCN_Msk;
  
      /* Enable ACMP interrupt */
      NVIC_EnableIRQ(ACMP_IRQn);
  
      while(1);
  
  }
  
  void ACMP_IRQHandler(void)
  {
      static uint32_t u32Cnt = 0;
  
      /* Clear ACMP0 interrupt flag */
      ACMP->CMPSR = ACMP_CMPSR_CMPF0_Msk;
      /* Check Comparator 0 Output Status */
      if(ACMP->CMPSR & ACMP_CMPSR_CO0_Msk)
          printf("ACMP0_P voltage > Band-gap voltage (%d)\n", u32Cnt);
      else
          printf("ACMP0_P voltage <= Band-gap voltage (%d)\n", u32Cnt);
  
      u32Cnt++;
  }
  
  
  void SYS_Init(void)
  {
      /*---------------------------------------------------------------------------------------------------------*/
      /* Init System Clock                                                                                       */
      /*---------------------------------------------------------------------------------------------------------*/
  
      /* Enable Internal RC 22.1184 MHz clock. Some peripherals select internal RC oscillator as default clock source. */
      CLK->PWRCON |= CLK_PWRCON_OSC22M_EN_Msk;
  
      /* Waiting for Internal RC clock ready */
      while(!(CLK->CLKSTATUS & CLK_CLKSTATUS_OSC22M_STB_Msk));
      
      /* Enable external 12 MHz XTAL */
      CLK->PWRCON |= CLK_PWRCON_XTL12M_EN_Msk;
  
      /* Waiting for clock ready */
      while(!(CLK->CLKSTATUS & CLK_CLKSTATUS_XTL12M_STB_Msk));
  
      /* Configure PLL */
      CLK->PLLCON = PLLCON_SETTING;
      while(!(CLK->CLKSTATUS & CLK_CLKSTATUS_PLL_STB_Msk));
      /* Select PLL as the system clock source */
      CLK->CLKSEL0 &= (~CLK_CLKSEL0_HCLK_S_Msk);
      CLK->CLKSEL0 |= CLK_CLKSEL0_HCLK_S_PLL;
      
      /* Select HXT as the clock source of UART */
      CLK->CLKSEL1 &= (~CLK_CLKSEL1_UART_S_Msk);
      CLK->CLKSEL1 |= CLK_CLKSEL1_UART_S_HXT;
  
      /* Enable UART and ACMP clock */
      CLK->APBCLK = CLK_APBCLK_UART0_EN_Msk | CLK_APBCLK_ACMP_EN_Msk;
  
      /* Update System Core Clock */
      /* User can use SystemCoreClockUpdate() to calculate SystemCoreClock and CyclesPerUs automatically. */
      SystemCoreClockUpdate();
  
  
      /*---------------------------------------------------------------------------------------------------------*/
      /* Init I/O Multi-function                                                                                 */
      /*---------------------------------------------------------------------------------------------------------*/
      /* Set PC.6 multi-function pin for ACMP0 positive input pin */
      SYS->GPC_MFP &= ~SYS_GPC_MFP_PC6_Msk;
      SYS->GPC_MFP |= SYS_GPC_MFP_PC6_ACMP0_P;
      SYS->ALT_MFP1 &= ~SYS_ALT_MFP1_PC6_Msk;
      SYS->ALT_MFP1 |= SYS_ALT_MFP1_PC6_ACMP0_P;
  
      /* Set PB multi-function pins for UART0 RXD, TXD and ACMP0 output */
      SYS->GPB_MFP &= ~(SYS_GPB_MFP_PB0_Msk | SYS_GPB_MFP_PB1_Msk | SYS_GPB_MFP_PB12_Msk);
      SYS->GPB_MFP |= SYS_GPB_MFP_PB0_UART0_RXD | SYS_GPB_MFP_PB1_UART0_TXD | SYS_GPB_MFP_PB12_ACMP0_O;
      SYS->ALT_MFP &= ~SYS_ALT_MFP_PB12_Msk;
      SYS->ALT_MFP |= SYS_ALT_MFP_PB12_ACMP0_O;
  
      /* Disable digital input path of analog pin ACMP0_P to prevent leakage */
      PC->OFFD |= (1 << 6) << GPIO_OFFD_OFFD_Pos;
  
  }
  
  void UART_Init(void)
  {
      /* Word length is 8 bits; 1 stop bit; no parity bit. */
      UART0->LCR = UART_LCR_WLS_Msk;
      /* Using mode 2 calculation: UART bit rate = UART peripheral clock rate / (BRD setting + 2) */
      /* UART peripheral clock rate 12MHz; UART bit rate 115200 bps. */
      /* 12000000 / 115200 bps ~= 104 */
      /* 104 - 2 = 0x66. */
      UART0->BAUD = UART_BAUD_DIV_X_EN_Msk | UART_BAUD_DIV_X_ONE_Msk | (0x66);
  }
  
  /*** (C) COPYRIGHT 2014 Nuvoton Technology Corp. ***/
  
  
  