Erasing flash memory?

The exact answer is 0x17 to divide by 24 as the divider FNx+1.

A more interesting question is "what happens if you get the frequency wrong?"For  several years I chose the 4Mhz MCLK instead of 1 MHz SMCLK then divided by 2 instead of 3. So far no ill effects but what will happen in the long term? Will the programs just fade away...........

While debugging the msp430f2274 with the IAR Embedded Workbench IDE,
I accidentally enabled 'Allow erase/write access to locked flash memory' and ''Allow erase/write access to BSL flash memory'.
(This can be found by right -clicking the project -> options -> debugger -> FET Debugger -> download.)

Now it seems that the 'factory calibrated value from flash' registers are also erased. Making it harder to calibrate the clock freq.

Is it possible to undo recent events?

Thanks a lot.

Mar

marino back said:

Is it possible to undo recent events?

Sure. It should be possible to restore the original values by opening the chip and doing an analysis on quantum level. There will likely be traces of the last programming left. However, the chip is gone then, and the replacement will come with its own set of calibration data.

In other words: no. Erased is erased. That's what erase means. Yo can reconstruct the values the same way TI initially has built them: run a softtware that compares the internal results with an external reference and calculate the the required calibration value (for reference calibration value) or step through the available DCO settings and compare the result with an external known clock source (for the clock calibration values). someone has released a program here in this forum that does the clock calibration. You should be able to locate it with the search function.

Jens-Michael,

Would you mind linking the post that has the program attached?

I was unsuccessful in several searches for this post and I am all but certain that the post is now gone.

I know it sounds dumb but I would really appreciate it if you helped me find this post.

Thank you for all you do for MSP, we are all greatful for your support.

MSP430F20xx Code Examples (slac080.zip) has the following.

//******************************************************************************
//  MSP430F20xx 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 F2xx 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 *//
//
//           MSP430F20xx
//         ---------------
//     /|\|            XIN|-
//      | |               | 32kHz
//      --|RST        XOUT|-
//        |               |
//        |           P1.0|--> LED
//        |           P1.4|--> SMLCK = target DCO
//
//  A. Dannenberg
//  Texas Instruments Inc.
//  May 2007
//  Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.42A
//******************************************************************************
#include "msp430x20x1.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
}

More room for me to make errors here! I used the default watch crystal load of 6pF on my MSP430F2418s.

I think most common watch crystals need 12.5pF ideally.

I have had 1 board out of some 1000s where the watch crystal sometimes gave the error flag set during initiallisation.

Maybe it was a tolerance issue - the load was on the low side of 6pF?  With 12.5pF it always initiallised OK.

Anyhow I suggest you make sure you select the correct load for safety. 

  BCSCTL3=XT2S_2+XCAP_3;            // increase to 12.5pF

OCY,

Thank you for picking up my post!

It's funny I was looking for a code example as reference for helping another customer with a crystal oscillator issue when I also stumbled across this same code example in the readme.

Your continued support on the MSP430 and E2E forums in general are also greatly appreciated keep up the good work!