STM32L431 mass erase over SWD not working

[user 143]

Hello,

I've created a custom PCB with a STM32F207 controller on it. With this board I want to address different targets using SWD. My targets are a STM32F407 and a STM32L431 controller. I implemented a custom SWD interface with Timer and DMA on my F207 controller and now I'm able to talk with my targets over their built-in SWD interface. For example I can read the UniqueID of the targets or write into the flash of them.

But I've got a problem with the mass erase of the flash. With the F407 the flash mass erase work fine. It took about 8 sec and then the hole flash is empty. But on the L431 it wont work.

Writing into the empty flash of the L431 works fine.

I take the following steps to perform a mass erase of the flash:

• Unlock the write access to the flash register (works, because the LOCK bit is not set anymore and I can write to the flash).
• Then I check if the BSY bit in the flash status register is set. When it's set, I wait until it's cleared.
• Then I'm clearing the ICEN and DCEN bits in the FLASH_ACR register. This is not mentioned in the reference manual, but ST is doing this in the HAL functions. But it makes no difference whether I delete the bits or not, deleting the flash does not work in either case.
• Now im clearing every error bit in the flash status register
• Setting the MER1 bit in the flash control register (and then read out the flash control register to check whether the bit has been set)
• And finally set the STRT bit in the FLASH_CR register

On the F407 this routine works fine. After setting the STRT bit it took about 8 sec. until the BSY flag is cleared. With the L431 on the other hand, mass erase should take only 22 ms (according to a presentation by ST). But it doesn't work at all.

Also the PGSERR bit is set in the FLASH_SR register on the L431. I don't understand the bit in this context, because I don't want to write, I want to delete.

Any ideas?

Thank you

[Uwe Bonnes]

Does your code look similar to:

       stm32l4_flash_unlock(t);

       /* Erase time is 25 ms. No need for a spinner.*/

       /* Flash erase action start instruction */

       stm32l4_flash_write32(t, FLASH_CR, action);

       stm32l4_flash_write32(t, FLASH_CR, action | FLASH_CR_STRT);

       /* Read FLASH_SR to poll for BSY bit */

       while (stm32l4_flash_read32(t, FLASH_SR) & FLASH_SR_BSY) {

               if(target_check_error(t)) {

                       return false;

               }

       }

       /* Check for error */

       uint16_t sr = stm32l4_flash_read32(t, FLASH_SR);

       if (sr & FLASH_SR_ERROR_MASK)

               return false;

       return true;

I have not heard of problems with that code.

[user 143 · Accepted solution]

Kind of, yes.

I've found my mistake. The PG bit in the FLASH_CR register was set. For the F407 this was not a problem, but the L431 had a problem with it. Wenn the PG bit is cleared, mass erase works as expected. Thank you!