请教一下关于MSP430F5255低功耗的问题。

使用MSP430F5255单片机，外围电路全部没有焊接，只接了晶振和外部滤波电容。系统使用的是外部晶振12M，所有IO口配置为输出，并且拉低。进入LPM3模式，测得的电流有350uA，和datasheet里面说的25uA差了10倍，请问是什么问题？

Ling Zhu2：

  用什么供电的？ 有LDO没？

晶振使能没有，默认应该不是用晶振的。

xiaoli：

回复 Ling Zhu2:

直接用直流稳压电源供电，晶振已经起振。有个奇怪的问题，就是进入LPM3模式，晶振居然还是起振的，但是SMCLK已经停止

Ling Zhu2：

回复 xiaoli:

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//******************************************************************************
//MSP430x552x Demo - Enters LPM3 with ACLK = LFXT1, REF0 disabled,//VUSB LDO and SLDO disabled, SVS disabled
//
//Description: Configure ACLK = LFXT1 and enters LPM3. Measure current.
//ACLK = LFXT1 = 32kHz, MCLK = SMCLK = default DCO
//
//MSP430F552x
//-----------------
///|\ |XIN|-
//||| 32kHz
//---|RSTXOUT|-
//||
//
//Bhargavi Nisarga
//Texas Instruments Inc.
//April 2009
//Built with CCSv4 and IAR Embedded Workbench Version: 4.21
//******************************************************************************
#include <msp430.h>int main(void)
{WDTCTL = WDTPW + WDTHOLD;// Stop watchdog timer// Enable XT1P5SEL |= BIT4+BIT5;// Port select XT1UCSCTL6 &= ~(XT1OFF);// XT1 OnUCSCTL6 |= XCAP_3;// Internal load cap// Loop until XT1 & DCO stabilizesdo{UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + DCOFFG);// Clear XT2,XT1,DCO fault flagsSFRIFG1 &= ~OFIFG;// Clear fault flags}while (SFRIFG1&OFIFG);// Test oscillator fault flagUCSCTL6 &= ~(XT1DRIVE_3);// Xtal is now stable, reduce drive// strength// Port ConfigurationP1OUT = 0x00;P2OUT = 0x00;P3OUT = 0x00;P4OUT = 0x00;P5OUT = 0x00;P6OUT = 0x00;P7OUT = 0x00;P8OUT = 0x00;PJOUT = 0x00;P1DIR = 0xFF;P2DIR = 0xFF;P3DIR = 0xFF;P4DIR = 0xFF;P5DIR = 0xFF;P6DIR = 0xFF;P7DIR = 0xFF;P8DIR = 0xFF;PJDIR = 0xFF;// Disable VUSB LDO and SLDOUSBKEYPID=0x9628;// set USB KEYandPID to 0x9628// access to USB config registers enabledUSBPWRCTL &= ~(SLDOEN+VUSBEN);// Disable the VUSB LDO and the SLDOUSBKEYPID=0x9600;// access to USB config registers disabled// Disable SVSPMMCTL0_H = PMMPW_H;// PMM PasswordSVSMHCTL &= ~(SVMHE+SVSHE);// Disable High side SVSSVSMLCTL &= ~(SVMLE+SVSLE);// Disable Low side SVS__bis_SR_register(LPM3_bits);// Enter LPM3__no_operation();// For debugger
}

xiaoli：

回复 Ling Zhu2:

用你的代码试了，测试电流有20mA。下面是我自己配置的代码。测试的是350uA。

//外部晶振12M
void SystemInit(void)
{__delay_cycles(5000);P5SEL |= BIT2 + BIT3;UCSCTL6 &= ~XT2OFF;do{UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + DCOFFG);// Clear XT2,XT1,DCO fault flagsSFRIFG1 &= ~OFIFG;// Clear fault flags}while (UCSCTL7 & XT2OFFG);// Test oscillator fault flagUCSCTL6 &= ~(XT2DRIVE_2);UCSCTL6 |= XT2DRIVE_1;UCSCTL4 |= SELM__XT2CLK + SELS__XT2CLK + SELA__REFOCLK;
}void GPIO_Init(void)
{P1DIR |= BIT0+BIT1+BIT2+BIT3+BIT4+BIT5+BIT6+BIT7;P2DIR |= BIT0+BIT1+BIT2+BIT3+BIT4+BIT5+BIT6+BIT7;P3DIR |= BIT0+BIT1+BIT2+BIT3+BIT4;P4DIR |= BIT0+BIT1+BIT2+BIT3+BIT4+BIT5+BIT6+BIT7;P6DIR |= BIT0+BIT1+BIT2+BIT3+BIT4+BIT5+BIT6+BIT7;P7DIR |= BIT0+BIT1+BIT2+BIT3+BIT4+BIT5;PJDIR |= BIT0+BIT1+BIT2+BIT3;P1OUT &= ~(BIT0+BIT1+BIT2+BIT3+BIT4+BIT5+BIT6+BIT7);P2OUT &= ~(BIT0+BIT1+BIT2+BIT3+BIT4+BIT5+BIT6+BIT7);P3OUT &= ~(BIT0+BIT1+BIT2+BIT3+BIT4);P4OUT &= ~(BIT0+BIT1+BIT2+BIT3+BIT4+BIT5+BIT6+BIT7);P6OUT &= ~(BIT0+BIT1+BIT2+BIT3+BIT4+BIT5+BIT6+BIT7);P7OUT &= ~(BIT0+BIT1+BIT2+BIT3+BIT4+BIT5);PJOUT &= ~(BIT0+BIT1+BIT2+BIT3);
}void Bsp_Init(void)
{SystemInit();GPIO_Init();_EINT();
}void main( void )
{Bsp_Init();__bis_SR_register(LPM3_bits);while(1);
}

Ling Zhu2：

回复 xiaoli:

 因为你用REFO了

建议 XT1 用32.768kHz晶振 作为 ACLK 的source。

xiaoli：

回复 Ling Zhu2:

不使用REFOCLK也是一样的，电流也是300多uA。请问进入低功耗模式LPM3，外部晶振是不是马上停止振动，还是说需要手动去关闭振动？发现把晶振关掉，功耗就降下去了

灰小子：

回复 xiaoli:

对功耗要求比较苛刻的话，完全没必要用外部晶振。

Ling Zhu2：