Programming Flash without HAL

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Hello, I am trying to make my own bootloader for STM32H743AIIx. Unluckly, I can't erase or program flash memory by my code. I unlock both of banks and see LOCK in FLASH_CR goes down. I put PG to up and write data until EOP flag is set. Despite the fact the full sequence was complete without any errors, I don't see any changes in memory monitor.

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Also, I have tried to use HAL. It could nor program nor erase too. I used next commands -

HAL_FLASH_Unlock();

FLASH_Erase_Sector(1, FLASH_BANK_1, FLASH_VOLTAGE_RANGE_1);

For erasing value 0x12345678 which was written to 0x0802000 address via memory browser. But nothing happend, the value was unchanged.

[TDK]

It helps if you show your actual code.

> For erasing value 0x12345678 which was written to 0x0802000 address via memory browser.

Address 0x0802000 isn't within the flash.