TI中文支持网Part Number:MSP430FR6972
软件清LFXTOFFG时，会导致单片机重启，我在用户手册上没有找到相关解释，是正常现象吗？如果是正常现象，能否避免软件清LFXTOFFG时，单片机重启呢？
Susan Yang：
yunlong zuo 说：软件清LFXTOFFG时
请问您是如何清的呢？能否给出相关代码？
另外您为何需要清除LFXTOFFG？
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yunlong zuo：
CSCTL5 &= ~(LFXTOFFG);
外部32768晶振遇到在设备组装时可能会受到轻微挤压导致，32768晶振瞬间故障，但是挤压过后又会恢复震荡，因为我的ACLK用的是外部的32768，单片机用户手册说，当外部晶振故障时会自动置位LFXTOFFG，并且自动切换到MODCLK代替32768供给ACLK，LFXTOFFG需要软件清除才会从MODCLK切回到32768。但是一执行CSCTL5 &= ~(LFXTOFFG);语句后单片机就自动重启一次。后来实验发现就算LFXTOFFG没置位，执行CSCTL5 &= ~(LFXTOFFG);也会重启一次。
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Susan Yang：
时钟系统似乎工作不正常。您能否将 MCLK 和 SMCLK 输出到 GPIO 并确定频率范围？
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yunlong zuo：
CSCTL0_H = CSKEY >> 8; CSCTL1 = DCOFSEL_1; CSCTL2 = SELA__LFXTCLK | SELS__DCOCLK | SELM__DCOCLK; CSCTL3 = DIVA__1 | DIVS__1 | DIVM__1; CSCTL4 = 0; CSCTL4 |= VLOOFF + SMCLKOFF + HFXTOFF; do { CSCTL5 &= ~(LFXTOFFG+ HFXTOFFG);// SFRIFG1 &= ~OFIFG; }while (SFRIFG1&OFIFG); CSCTL5 &= ~(ENSTFCNT1 + ENSTFCNT2); CSCTL6 &=~( ACLKREQEN|MCLKREQEN|SMCLKREQEN); CSCTL0_H = 0;
这是我的时钟配置，MCLK是用的DCOCLK,您要我在什么情况下，是把LFXTCLK输出吗？
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Susan Yang：
yunlong zuo 说：是把LFXTCLK输出吗？
是的，您的理解是正确的。
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yunlong zuo：
正常运行时32.75K–32.81K
晶振受挤压后自动跳到modclk时是36.98K–37.0K
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Susan Yang：
谢谢您的反馈。
请您试一下下面的代码能否正常运行，而不会复位
/* --COPYRIGHT--,BSD_EX* Copyright (c) 2014, Texas Instruments Incorporated* All rights reserved.** Redistribution and use in source and binary forms, with or without* modification, are permitted provided that the following conditions* are met:** *Redistributions of source code must retain the above copyright*notice, this list of conditions and the following disclaimer.** *Redistributions in binary form must reproduce the above copyright*notice, this list of conditions and the following disclaimer in the*documentation and/or other materials provided with the distribution.** *Neither the name of Texas Instruments Incorporated nor the names of*its contributors may be used to endorse or promote products derived*from this software without specific prior written permission.** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.**********************************************************************************MSP430 CODE EXAMPLE DISCLAIMER** MSP430 code examples are self-contained low-level programs that typically* demonstrate a single peripheral function or device feature in a highly* concise manner. For this the code may rely on the device's power-on default* register values and settings such as the clock configuration and care must* be taken when combining code from several examples to avoid potential side* effects. Also see www.ti.com/grace for a GUI- and www.ti.com/msp430ware* for an API functional library-approach to peripheral configuration.** --/COPYRIGHT--*/ //****************************************************************************** //MSP430FR6x7x Demo - Output 32768Hz crystal on XT1 and observe failsafe // //Description: Configure ACLK = LFXT1 and enter LPM3. //To observe failsafe behavior short the crystal briefly on the target board. //This will cause an NMI to occur. P1.0 is toggled inside the NMI ISR. //Once the fault flag is cleared XT1 operation continues from 32768Hz crystal //Otherwise ACLK defaults to LFMODCLK (~37.5KHz). //ACLK = LFXT1 = 32kHz, MCLK = SMCLK = 1MHz // //MSP430FR6972 //--------------- ///|\|XIN|- //| || 32KHz Crystal //--|RSTXOUT|- //|| //|PJ.2|---> ACLK = 32.768kHz (or 37.5kHz during LFXTOFFG) //|P7.4|---> SMCLK = MCLK = 1MHz //|P1.0|---> LED // //Andreas Dannenberg //Texas Instruments Inc. //September 2014 //Built with IAR Embedded Workbench V5.60 & Code Composer Studio V6.0 //****************************************************************************** #include <msp430.h>int main(void) {WDTCTL = WDTPW | WDTHOLD;// GPIO SetupP1OUT = 0;P1DIR = BIT0;// For LEDPJDIR |= BIT2;PJSEL0 |= BIT2;// Output ACLKPJSEL1 &= ~BIT2;P7DIR |= BIT4;P7SEL0 |= BIT4;P7SEL1 |= BIT4;// Output SMCLKPJSEL0 |= BIT4 | BIT5;// For XT1// Disable the GPIO power-on default high-impedance mode to activate// previously configured port settingsPM5CTL0 &= ~LOCKLPM5;// Clock System SetupCSCTL0_H = CSKEY >> 8;// Unlock CS registersCSCTL1 = DCOFSEL_0;// Set DCO to 1MHzCSCTL2 = SELA__LFXTCLK | SELS__DCOCLK | SELM__DCOCLK;CSCTL3 = DIVA__1 | DIVS__1 | DIVM__1;// Set all dividersCSCTL4 &= ~LFXTOFF;do{CSCTL5 &= ~LFXTOFFG;// Clear XT1 fault flagSFRIFG1 &= ~OFIFG;}while (SFRIFG1&OFIFG);// Test oscillator fault flag// Now that osc is running enable fault interruptSFRIE1 |= OFIE;__bis_SR_register(LPM0_bits);// Wait in LPM0 for fault flag }#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__) #pragma vector=UNMI_VECTOR __interrupt void UNMI_ISR(void) #elif defined(__GNUC__) void __attribute__ ((interrupt(UNMI_VECTOR))) UNMI_ISR (void) #else #error Compiler not supported! #endif {do{// set a breakpoint on the line below to observe XT1 operating from VLO// when the breakpoint is hit during a crystal faultCSCTL5 &= ~LFXTOFFG;// Clear XT1 fault flagSFRIFG1 &= ~OFIFG;P1OUT |= BIT0;__delay_cycles(25000);// time for flag to get set again}while (SFRIFG1&OFIFG);// Test oscillator fault flagP1OUT &= ~BIT0; }
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yunlong zuo：
能够正常运行不重启，下图是P1.0波形
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yunlong zuo：
上午又做实验应该是找到原因了
我的时钟初始化代码中
第一条语句解锁，然后最后一条又相当于锁了时钟的寄存器，手册里边说的是，
CSKEY password. Must always be written with A5h; a PUC is generated if anyother value is written. Always reads as 96h. After the correct password is written,all CS registers are available for writing.
相当于我再后边的程序没有解锁，直接这样写CSCTL5 &= ~(LFXTOFFG);，导致了一个PUC，所以只要执行这个就复位。
后来改了一下清LFXTOFFG的后边程序的代码
CSCTL0_H = CSKEY >> 8; do { CSCTL5 &= ~(LFXTOFFG+ HFXTOFFG);// SFRIFG1 &= ~OFIFG; }while (SFRIFG1&OFIFG); CSCTL0_H = 0;
这样就OK了，不重启
再次感谢您抽时间给我解答问题，没有您的帮助我还不知道啥时候能找出问题所在，谢谢！！！！！
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Susan Yang：
谢谢您的分享！很高兴您能解决问题
