Stop iwdg in halt mode on STM8L051F3

[PRasm.3]

Hey

I have tried to use the option byte to stop the iwdg when i enter halt.

I can see that i manage to set the WDG_HALTin option byte 3.

But the watchdog still resets the MCU after i enter halt.

Please help me, cant i do it? If so then how do i read that from the documentation.

If i can what am i doing wrong?

I can reproduce the problem with this code:

void halt_test(void) {
    // switch to 16MHz (default is 2MHz)
    sfr_CLK.CKDIVR.byte = 0x00;
 
    // Setup LED
    sfr_PORTB.DDR.DDR2 = 1; // input(=0) or output(=1)
    sfr_PORTB.CR1.C12 = 1;  // input: 0=float, 1=pull-up; output: 0=open-drain, 1=push-pull
 
    // Disable LED
    sfr_PORTB.ODR.ODR2 = 1;
 
    for (uint32_t i = 0; i < 600000; i++) {
        NOP();
    }
 
    // unlock w/e access to EEPROM & option bytes
    sfr_FLASH.DUKR.byte = 0xAE;
    sfr_FLASH.DUKR.byte = 0x56;
 
    // wait until access granted
    while (!(sfr_FLASH.IAPSR.DUL))
        ;
 
    // Enable write to option bytes
    sfr_FLASH.CR2.OPT = 1;
 
    // Set IWDG_HALT bit
    sfr_OPT.OPT3.byte = 0b10;
 
    // wait until end of programming
    while (!(sfr_FLASH.IAPSR.EOP))
        ;
 
    // Disable write to option bytes
    sfr_FLASH.CR2.OPT = 0;
 
    // lock EEPROM again against accidental erase/write
    sfr_FLASH.IAPSR.DUL = 0;
 
    // start IDWG (must be the first value written to this register, see UM)
    sfr_IWDG.KR.byte = (uint8_t)0xCC;
 
    // unlock write access to prescaler and reload registers
    sfr_IWDG.KR.byte = (uint8_t)0x55;
 
    sfr_IWDG.PR.PR = 6;
 
    // set timeout period 0xff = 1724.63ms according to RM0031
    sfr_IWDG.RLR.byte = 0xff;
 
    // start IDWG
    sfr_IWDG.KR.byte = (uint8_t)0xCC;
 
    // Enable LED
    sfr_PORTB.ODR.ODR2 = 0;
 
    ENTER_HALT();
}

[PRasm.3]

No worries, i just saw you listed as an employee i guessed you had access to the board.

Do you know how to get in contact with somebody at st that have access to the chip?

[Peter BENSCH]

Unfortunately no, the only options are your local distributor or OnLine Support OLS where you can open a personal ticket.

However, the STM8 are already set to NRND (Not Recommended for New Design), so there are practically no resources left for this obsolete technology.

Good luck!

Regards

/Peter

[AA1]

Are you sure the watchdog resets while in halt?

Maybe program doesn't stop in halt.

[PRasm.3]

I think i found the problem, but im not entirely sure why.

For start watchdog i set the KR register to CC in the code example. If i set it to AA instead everything seems to work as expected.

Would anybody know why that change would matter? I guess by reading the datasheet AA makes more sense but its not clear to me

[AA1]

Maybe value AA doesn't start watchdog. So reset doesn't occur.

From datasheet value AA starts watchdog, value CC refreshes watchdog.

[AA1]

Correction:

Maybe value AA doesn't start watchdog. So reset doesn't occur.

From datasheet value CC starts watchdog, value AA refreshes watchdog.