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
}
