找到了。time_delay_ms(30);按键里面这个函数,
void time_delay_ms(unsigned int count_val)
{
/* Make sure the clock to the LPTMR is enabled */
SIM_SCGC5|=SIM_SCGC5_LPTMR_MASK;
/* Reset LPTMR settings */
LPTMR0_CSR=0;
/* Set the compare value to the number of ms to delay */
LPTMR0_CMR = count_val;
/* Set up LPTMR to use 1kHz LPO with no prescaler as its clock source */
LPTMR0_PSR = LPTMR_PSR_PCS(1)|LPTMR_PSR_PBYP_MASK;
/* Start the timer */
LPTMR0_CSR |= LPTMR_CSR_TEN_MASK;
/* Wait for counter to reach compare value */
while (!(LPTMR0_CSR & LPTMR_CSR_TCF_MASK));
/* Disable counter and Clear Timer Compare Flag */
LPTMR0_CSR &= ~LPTMR_CSR_TEN_MASK;