STM32F407 Flash sector auto cleared after programming

Question

I've tried to do flash logger function for my device based on STM32f407 and found some problem with flash:

If I uncomment function for clear sector, after load program my dummy data on first page is cleared before i start.

what I've done :

1) In .ld file I've define some sections:

MEMORY
{
    FLASH_S0 (rx)   : ORIGIN = 0x08000000, LENGTH = 16K
    FLASH_S1 (rx)   : ORIGIN = 0x08004000, LENGTH = 16K             /* Reserved for OS*/
    FLASH_S2 (rx)   : ORIGIN = 0x08008000, LENGTH = 16K             /* LogPage1 */
    FLASH_S3 (rx)   : ORIGIN = 0x0800C000, LENGTH = 16K             /* LogPage2 */
    ...
in SECTIONS :

.logPage1 :
    {
        . = ALIGN(4);
         KEEP(*(.logPage1)) /*Startup code */
        . = ALIGN(4);
    } >FLASH_S2

        .logPage2 :
    {
        . = ALIGN(4);
        KEEP(*(.logPage2)) /* Startup code */
        . = ALIGN(4);
    } >FLASH_S3 

2) in code create two const data arrays:

volatile const uint32_t __attribute__((section (".logPage1"))) log_data_page1[2] = {0xDEADBEEF, 0xDEADBEEF};
volatile const uint32_t __attribute__((section (".logPage2"))) log_data_page2[2] = {0xDEADBEEF, 0xDEADBEEF};

3)for test reason there was defined some data in header :

#define LOGPAGENUM   2
#define LOGDATACOUNT 2
#define LOGDATASIZE  FLASHLogDataSize_32b
#define FLASHPAGESIZE 0x4000
#define FLASHSTARTADDR 0x08000000
#define LOGFIRSTPAGE  2
#define LOGSECONDPAGE 3
#define SECTORCOUNT 12

4) and there is functions:

BOOL FLASHClear (uint8_t clearSector){
    FLASH_Status status;
    if(clearSector >= SECTORCOUNT) return FALSE;

      FLASH_Unlock();

      while(FLASH->SR & FLASH_SR_BSY) {}
      {
            uint32_t Temp = FLASH->CR;

            Temp &= ~(0xFUL << 3); // FLASH_CR_SNB [3:6]
            Temp |=  (clearSector << 3);

            Temp |= FLASH_CR_SER;

            FLASH->CR = Temp;
        }
      FLASH->CR |= FLASH_CR_STRT;
      while(FLASH->SR & FLASH_SR_BSY) {}
      FLASH->CR &= ~FLASH_CR_SER;

      FLASH_Lock();
    return status;
}

and where it is called:

FLASHSectionPage FLASHLog_ActivePageSrch(TFLASHSector sectors[], uint32_t pageSize, uint8_t dataSize){
    FLASHSectionPage page = FLASHSection_Page_None;

    uint32_t headData ;
    uint32_t tailData ;

    uint8_t scanPage = (uint8_t) page;

// no While for less memory and CPU usage
         scanPage = NextSectionPage(scanPage); // FLASHSection_Page_None в LOGFIRSTPAGE
         headData = FLASHRead(sectors[scanPage].From);
         tailData = FLASHRead(sectors[scanPage].From+ pageSize - dataSize);

    if ( ((headData & EMPTYWORD) != EMPTYWORD) &&
         ((tailData & EMPTYWORD) == EMPTYWORD)  ){
                page = (FLASHSectionPage)scanPage;
            }
    else {
        scanPage = NextSectionPage(scanPage);   // LOGFIRSTPAGE в LOGSECONDPAGE
        headData = FLASHRead(sectors[scanPage].From);
        tailData = FLASHRead(sectors[scanPage].From+ pageSize - dataSize);

        if ( ((headData & EMPTYWORD) != EMPTYWORD) &&
             ((tailData & EMPTYWORD) == EMPTYWORD)  ){
                    page = (FLASHSectionPage)scanPage;
                }
        else {

// both page is full clear first and mark as active scanPage = NextSectionPage(scanPage); // LOGSECONDPAGE to LOGFIRSTPAGE FLASHClear (scanPage); page = (FLASHSectionPage)scanPage; } } return page; }

5) call of second function is like these:

page = FLASHLog_ActivePageSrch( sectors, LOGDATACOUNT * 0x4 ,  0x4 );

6) sector is constatn array - map of MCU flash: TFLASHLogMap FLASHLog;

static const TFLASHSector sectors[] = {
    // STM32F40x, STM32F41x, STM32F42x, STM32F43x
    { 0x08000000UL, 0x08003FFFUL,  0 }, // 16 kB
    { 0x08004000UL, 0x08007FFFUL,  1 }, // 16 kB
    { 0x08008000UL, 0x0800BFFFUL,  2 }, // 16 kB
    { 0x0800C000UL, 0x0800FFFFUL,  3 }, // 16 kB
    { 0x08010000UL, 0x0801FFFFUL,  4 }, // 64 kB
    { 0x08020000UL, 0x0803FFFFUL,  5 }, // 128 kB
    { 0x08040000UL, 0x0805FFFFUL,  6 }, // 128 kB
    { 0x08060000UL, 0x0807FFFFUL,  7 }, // 128 kB
    { 0x08080000UL, 0x0809FFFFUL,  8 }, // 128 kB
    { 0x080A0000UL, 0x080BFFFFUL,  9 }, // 128 kB
    { 0x080C0000UL, 0x080DFFFFUL, 10 }, // 128 kB
    { 0x080E0000UL, 0x080FFFFFUL, 11 }, // 128 kB
};

And so, if i've comment this line FLASH->CR |= FLASH_CR_STRT; after compile and debug I can see in memory in address 0x08008000 and 0x0800c000

DEADBEEF DEADBEEF

but if I just uncomment it and start debug there will be these data:

0x08008000 > FFFFFFFF FFFFFFFF

0x0800c000 > DEADBEEF DEADBEEF

Please help me to understand how is code for cleare page is done before I start, and how can I fix it

Answer 1

Problem was located - it is CoIDE DeBugger settings, I've add some Led blink on load and work cycle, so I've seen that while I load code in debug mode from CoIDE CPU is working and do code for 3-4 sec, so clearing data is normal reaction of code