MSP430F6459: MSP430F6459 ACLK shutdown in LPM3 mode

Hi everyone,

In LPM3 mode, ACLK should still work. But the following code in MSP430F6459 tells it will shut down ACLK( source from XT1=32KHz).

Besides, if my PCBA connet with MSP-Fet430UIF, ACLK is fine(LPM3).

Need your help on this.

Thanks.

Best Regards,

SeaFesse

#include <msp430f6459.h>

void main(void)
{
    
    WDTCTL = WDTPW | WDTHOLD;                 // Stop WDT
    
    P1DIR |= BIT0;
    P1SEL |= BIT0;      //P1.0----ACLK output
    
    PJDIR |= BIT2;
    // PJSEL &=~BIT2;
    
    while(BAKCTL & LOCKBAK)                    // Unlock XT1 pins for operation
        BAKCTL &= ~(LOCKBAK);
    

    // Setup UCS
    UCSCTL3 |= SELREF__XT1CLK;                   // Set DCO FLL reference = XT1
    UCSCTL4 |= SELA__XT1CLK;                     // Set ACLK = XT1
    
    __bis_SR_register(SCG0);               // Disable the FLL control loop
    UCSCTL0 = 0x0000;                      // Set lowest possible DCOx, MODx
    UCSCTL1 = DCORSEL_5;                   // Select DCO range 16MHz operation
    UCSCTL2 = FLLD_1 | 243;                // Set DCO Multiplier for 8MHz
    // (N + 1) * FLLRef = Fdco
    // (243 + 1) * 32768 = 8MHz
    // Set FLL Div = fDCOCLK/2
    __bic_SR_register(SCG0);               // Enable the FLL control loop
    
    // Worst-case settling time for the DCO when the DCO range bits have been
    // changed is n x 32 x 32 x f_MCLK / f_FLL_reference. See UCS chapter in 5xx
    // UG for optimization.
    // 32 x 32 x 8 MHz / 32,768 Hz = 250000 = MCLK cycles for DCO to settle
    __delay_cycles(250000);
    
    // Loop until XT1, XT2 & DCO fault flag is cleared
    do
    {
        UCSCTL7 &= ~(XT2OFFG | XT1LFOFFG | DCOFFG);
        // Clear XT2,XT1,DCO fault flags
        SFRIFG1 &= ~OFIFG;                 // Clear fault flags
    } while (SFRIFG1 & OFIFG);             // Test oscillator fault flag
    

    
    
    
    
    while(1)
    {
        __bis_SR_register(LPM3_bits | GIE);       // Enter LPM0, interrupts enabled
        __no_operation();                         // For debugger
        
    }
    
}