TI中文支持网使用了如下程序，结果SMCLK的输出非常奇怪，根本就不是方波
//******************************************************************************
// MSP430G2xx1 Demo – DCO Calibration Constants Programmer
//
// NOTE: THIS CODE REPLACES THE TI FACTORY-PROGRAMMED DCO CALIBRATION
// CONSTANTS LOCATED IN INFOA WITH NEW VALUES. USE ONLY IF THE ORIGINAL
// CONSTANTS ACCIDENTALLY GOT CORRUPTED OR ERASED.
//
// Description: This code re-programs the G2xx1 DCO calibration constants.
// A software FLL mechanism is used to set the DCO based on an external
// 32kHz reference clock. After each calibration, the values from the
// clock system are read out and stored in a temporary variable. The final
// frequency the DCO is set to is 1MHz, and this frequency is also used
// during Flash programming of the constants. The program end is indicated
// by the blinking LED.
// ACLK = LFXT1/8 = 32768/8, MCLK = SMCLK = target DCO
// //* External watch crystal installed on XIN XOUT is required for ACLK *//
//
// MSP430G2xx1
// —————
// /|\| XIN|-
// | | | 32kHz
// –|RST XOUT|-
// | |
// | P1.0|–> LED
// | P1.4|–> SMLCK = target DCO
//
// A. Dannenberg
// Texas Instruments Inc.
// May 2010
// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 3.42A
//******************************************************************************
#include "msp430g2231.h"
#define DELTA_1MHZ 244 // 244 x 4096Hz = 999.4Hz
#define DELTA_8MHZ 1953 // 1953 x 4096Hz = 7.99MHz
#define DELTA_12MHZ 2930 // 2930 x 4096Hz = 12.00MHz
#define DELTA_16MHZ 3906 // 3906 x 4096Hz = 15.99MHz
unsigned char CAL_DATA[8]; // Temp. storage for constants
volatile unsigned int i;
int j;
char *Flash_ptrA; // Segment A pointer
void Set_DCO(unsigned int Delta);
void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
for (i = 0; i < 0xfffe; i++); // Delay for XTAL stabilization
P1OUT = 0x00; // Clear P1 output latches
P1SEL = 0x10; // P1.4 SMCLK output
P1DIR = 0x11; // P1.0,4 output
j = 0; // Reset pointer
Set_DCO(DELTA_16MHZ); // Set DCO and obtain constants
CAL_DATA[j++] = DCOCTL;
CAL_DATA[j++] = BCSCTL1;
Set_DCO(DELTA_12MHZ); // Set DCO and obtain constants
CAL_DATA[j++] = DCOCTL;
CAL_DATA[j++] = BCSCTL1;
Set_DCO(DELTA_8MHZ); // Set DCO and obtain constants
CAL_DATA[j++] = DCOCTL;
CAL_DATA[j++] = BCSCTL1;
Set_DCO(DELTA_1MHZ); // Set DCO and obtain constants
CAL_DATA[j++] = DCOCTL;
CAL_DATA[j++] = BCSCTL1;
Flash_ptrA = (char *)0x10C0; // Point to beginning of seg A
FCTL2 = FWKEY + FSSEL0 + FN1; // MCLK/3 for Flash Timing Generator
FCTL1 = FWKEY + ERASE; // Set Erase bit
FCTL3 = FWKEY + LOCKA; // Clear LOCK & LOCKA bits
*Flash_ptrA = 0x00; // Dummy write to erase Flash seg A
FCTL1 = FWKEY + WRT; // Set WRT bit for write operation
Flash_ptrA = (char *)0x10F8; // Point to beginning of cal consts
for (j = 0; j < 8; j++)
*Flash_ptrA++ = CAL_DATA[j]; // re-flash DCO calibration data
FCTL1 = FWKEY; // Clear WRT bit
FCTL3 = FWKEY + LOCKA + LOCK; // Set LOCK & LOCKA bit
while (1)
{
P1OUT ^= 0x01; // Toggle LED
for (i = 0; i < 0x4000; i++); // SW Delay
}
}
void Set_DCO(unsigned int Delta) // Set DCO to selected frequency
{
unsigned int Compare, Oldcapture = 0;
BCSCTL1 |= DIVA_3; // ACLK = LFXT1CLK/8
TACCTL0 = CM_1 + CCIS_1 + CAP; // CAP, ACLK
TACTL = TASSEL_2 + MC_2 + TACLR; // SMCLK, cont-mode, clear
while (1)
{
while (!(CCIFG & TACCTL0)); // Wait until capture occured
TACCTL0 &= ~CCIFG; // Capture occured, clear flag
Compare = TACCR0; // Get current captured SMCLK
Compare = Compare – Oldcapture; // SMCLK difference
Oldcapture = TACCR0; // Save current captured SMCLK
if (Delta == Compare)
break; // If equal, leave "while(1)"
else if (Delta < Compare)
{
DCOCTL–; // DCO is too fast, slow it down
if (DCOCTL == 0xFF) // Did DCO roll under?
if (BCSCTL1 & 0x0f)
BCSCTL1–; // Select lower RSEL
}
else
{
DCOCTL++; // DCO is too slow, speed it up
if (DCOCTL == 0x00) // Did DCO roll over?
if ((BCSCTL1 & 0x0f) != 0x0f)
BCSCTL1++; // Sel higher RSEL
}
}
TACCTL0 = 0; // Stop TACCR0
TACTL = 0; // Stop Timer_A
BCSCTL1 &= ~DIVA_3; // ACLK = LFXT1CLK
}
Susan Yang：
建议您使用下面的程序测试一下
/* --COPYRIGHT--,BSD_EX* Copyright (c) 2012, 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--*/ //****************************************************************************** //MSP430G2xx1 Demo - Basic Clock, Output Buffered clocks with preloaded DCO //calibration constants for BCSCTL1 and DCOCTL. ////Description: Buffer ACLK on P1.0, default SMCLK(DCO) on P1.4 and MCLK/10 on //P1.1. DCO is software selectable to 1, 8, 12, or 16Mhz using calibration //contstants in INFOA. // //ACLK = LFXT1 = 32768, MCLK = SMCLK = Selectable at 1, 8, 12 or 16Mhz ////* External watch crystal installed on XIN XOUT is required for ACLK *//// //* By default, the MSP430 uses XT1 to source ACLK; P2.6/7 configured////* automatically. //MSP430G2xx1 //----------------- ///|\|P2.6/XIN|- //| || 32kHz //--|RSTP2.7/XOUT|- //|| //|P1.4/SMCLK|-->SMCLK = Default DCO //|P1.1|-->MCLK/10 = DCO/10 //|P1.0/ACLK|-->ACLK = 32kHz ////D. Dang //Texas Instruments Inc. //October 2010 //Built with IAR Embedded Workbench Version: 3.42A //******************************************************************************#include <msp430.h>int main(void) {WDTCTL = WDTPW +WDTHOLD;// Stop Watchdog Timer//1Mhzif (CALBC1_1MHZ==0xFF)// If calibration constants erased{while(1);// do not load, trap CPU!!}DCOCTL = 0;// Select lowest DCOx and MODx settingsBCSCTL1 = CALBC1_1MHZ;// Set rangeDCOCTL = CALDCO_1MHZ;// Set DCO step + modulation *//* //8Mhzif (CALBC1_8MHZ==0xFF)// If calibration constants erased{while(1);// do not load, trap CPU!!}DCOCTL = 0;// Select lowest DCOx and MODx settingsBCSCTL1 = CALBC1_8MHZ;// Set rangeDCOCTL = CALDCO_8MHZ;// Set DCO step + modulation *//* //12Mhzif (CALBC1_12MHZ==0xFF)// If calibration constants erased{while(1);// do not load, trap CPU!!}DCOCTL = 0;// Select lowest DCOx and MODx settingsBCSCTL1 = CALBC1_12MHZ;// Set rangeDCOCTL = CALDCO_12MHZ;// Set DCO step + modulation*//* //16Mhzif (CALBC1_16MHZ==0xFF)// If calibration constants erased{while(1);// do not load, trap CPU!!}DCOCTL = 0;// Select lowest DCOx and MODx settingsBCSCTL1 = CALBC1_16MHZ;// Set rangeDCOCTL = CALDCO_16MHZ;// Set DCO step + modulation*/P1DIR |= 0x13;// P1.0,1 and P1.4 outputsP1SEL |= 0x11;// P1.0,4 ACLK, SMCLK outputwhile(1){P1OUT |= 0x02;// P1.1 = 1P1OUT &= ~0x02;// P1.1 = 0} }
user6372742：
回复 Susan Yang:
我使用的芯片是MSP430F2131，我查看芯片手册，发现该芯片没有XT2时钟源，而使用高频时钟只能采用DCOCLK。
我需要一个12M的时钟源，但是出厂的DCOCLK精度达不到我们的要求，因此我们需要对DCOCLK校准，然而主时钟也得用DCOCLK，所以好像达不到预期的效果，请问这种情况我们还可以采取什么手段来校准DCO时钟呢
Susan Yang：
回复 user6372742:
我们继续在下面的链接中讨论
e2echina.ti.com/…/192782
