关于M480增强型PWM的同步启动用法的疑问

/**************************************************************************//**
* @file     main.c
* @version  V3.00
* @brief    Demonstrate how to use EPWM counter synchronous start function.
*
* @CopyRight (C) 2016 Nuvoton Technology Corp. All rights reserved.
******************************************************************************/
#include
#include "NuMicro.h"

#define PLL_CLOCK       192000000



void SYS_Init(void)
{

    /* Set XT1_OUT(PF.2) and XT1_IN(PF.3) to input mode */
    PF->MODE &= ~(GPIO_MODE_MODE2_Msk | GPIO_MODE_MODE3_Msk);

    /* Enable HXT clock (external XTAL 12MHz) */
    CLK_EnableXtalRC(CLK_PWRCTL_HXTEN_Msk);

    /* Wait for HXT clock ready */
    CLK_WaitClockReady(CLK_STATUS_HXTSTB_Msk);

    /* Set core clock as PLL_CLOCK from PLL */
    CLK_SetCoreClock(PLL_CLOCK);

    /* Set PCLK0 = PCLK1 = HCLK/2 */
    CLK->PCLKDIV = (CLK_PCLKDIV_PCLK0DIV2 | CLK_PCLKDIV_PCLK1DIV2);

    /* Enable IP module clock */
    CLK_EnableModuleClock(EPWM0_MODULE);

    /* EPWM clock frequency is set double to PCLK: select EPWM module clock source as PLL */
    CLK_SetModuleClock(EPWM0_MODULE, CLK_CLKSEL2_EPWM0SEL_PLL, (uint32_t)NULL);

    /* Enable UART module clock */
    CLK_EnableModuleClock(UART0_MODULE);

    /* Select UART module clock source as HXT and UART module clock divider as 1 */
    CLK_SetModuleClock(UART0_MODULE, CLK_CLKSEL1_UART0SEL_HXT, CLK_CLKDIV0_UART0(1));

    /* Update System Core Clock */
    SystemCoreClockUpdate();


    /* Set GPB multi-function pins for UART0 RXD and TXD */
    SYS->GPB_MFPH &= ~(SYS_GPB_MFPH_PB12MFP_Msk | SYS_GPB_MFPH_PB13MFP_Msk);
    SYS->GPB_MFPH |= (SYS_GPB_MFPH_PB12MFP_UART0_RXD | SYS_GPB_MFPH_PB13MFP_UART0_TXD);

    /* Set PA.0~5 multi-function pin for EPWM0 channel 0~5 */
    SYS->GPA_MFPL = (SYS->GPA_MFPL & ~SYS_GPA_MFPL_PA0MFP_Msk) | SYS_GPA_MFPL_PA0MFP_EPWM0_CH5;
    SYS->GPA_MFPL = (SYS->GPA_MFPL & ~SYS_GPA_MFPL_PA1MFP_Msk) | SYS_GPA_MFPL_PA1MFP_EPWM0_CH4;
    SYS->GPA_MFPL = (SYS->GPA_MFPL & ~SYS_GPA_MFPL_PA2MFP_Msk) | SYS_GPA_MFPL_PA2MFP_EPWM0_CH3;
    SYS->GPA_MFPL = (SYS->GPA_MFPL & ~SYS_GPA_MFPL_PA3MFP_Msk) | SYS_GPA_MFPL_PA3MFP_EPWM0_CH2;
    SYS->GPA_MFPL = (SYS->GPA_MFPL & ~SYS_GPA_MFPL_PA4MFP_Msk) | SYS_GPA_MFPL_PA4MFP_EPWM0_CH1;
    SYS->GPA_MFPL = (SYS->GPA_MFPL & ~SYS_GPA_MFPL_PA5MFP_Msk) | SYS_GPA_MFPL_PA5MFP_EPWM0_CH0;
}

void UART0_Init()
{
    /* Configure UART0 and set UART0 baud rate */
    UART_Open(UART0, 115200);
}

int32_t main(void)
{
    /* Init System, IP clock and multi-function I/O
       In the end of SYS_Init() will issue SYS_LockReg()
       to lock protected register. If user want to write
       protected register, please issue SYS_UnlockReg()
       to unlock protected register if necessary */

    /* Unlock protected registers */
    SYS_UnlockReg();

    /* Init System, IP clock and multi-function I/O */
    SYS_Init();

    /* Lock protected registers */
    SYS_LockReg();

    /* Init UART to 115200-8n1 for print message */
    UART0_Init();

    printf("\n\nCPU @ %dHz(PLL@ %dHz)\n", SystemCoreClock, PllClock);
    printf("EPWM0 clock is from %s\n", (CLK->CLKSEL2 & CLK_CLKSEL2_EPWM0SEL_Msk) ? "CPU" : "PLL");
    printf("+------------------------------------------------------------------------+\n");
    printf("|                          EPWM Driver Sample Code                        |\n");
    printf("|                                                                        |\n");
    printf("+------------------------------------------------------------------------+\n");
    printf("  This sample code will output waveform with EPWM0  channel 0~5 at the same time.\n");
    printf("  I/O configuration:\n");
    printf("    waveform output pin: EPWM0_CH0(PA.5), EPWM0_CH1(PA.4), EPWM0_CH2(PA.3), EPWM0_CH3(PA.2), EPWM0_CH4(PA.1), EPWM0_CH5(PA.0)\n");


    /* EPWM0 channel 0~5 frequency and duty configuration are as follows */
    EPWM_ConfigOutputChannel(EPWM0, 0, 1000, 50);
    EPWM_ConfigOutputChannel(EPWM0, 1, 1000, 50);
    EPWM_ConfigOutputChannel(EPWM0, 2, 1000, 50);
    EPWM_ConfigOutputChannel(EPWM0, 3, 1000, 50);
    EPWM_ConfigOutputChannel(EPWM0, 4, 1000, 50);
    EPWM_ConfigOutputChannel(EPWM0, 5, 1000, 50);

    /* Enable counter synchronous start function for EPWM0 channel 0~5 */
    EPWM_ENABLE_TIMER_SYNC(EPWM0, 0x3F, EPWM_SSCTL_SSRC_EPWM0);

    /* Enable output of EPWM0 channel 0~5 */
    EPWM_EnableOutput(EPWM0, 0x3F);

    printf("Press any key to start.\n");
    getchar();

    /* Trigger EPWM counter synchronous start by EPWM0 */
    EPWM_TRIGGER_SYNC_START(EPWM0);

    printf("Done.");
    while(1);

}

/*** (C) COPYRIGHT 2016 Nuvoton Technology Corp. ***/