STM8 EEPROM unlocking is repeatable

After the STM8 EEPROM is reset, if you want to write data, you must unlock it first, otherwise you will not be able to write data. Unlocking means writing to FLASH_DUKR in sequence:

The first hardware key: 0xAE

Second hardware key: 0x56

Two bytes of data.

At this time, the DUL bit in FLASH_IAPSR will become 1, indicating that the EEPROM has been successfully unlocked and can be written. If the DUL bit is not 1, the key can be written repeatedly in sequence until the DUL bit is 1.

But the manual says this:

Chinese manual:

2. If the key is entered incorrectly, the application can try to re-enter the two MASS keys to
unlock .

4. If the key is entered incorrectly, the DATA EEPROM area will remain write-protected until the next system reset.

Before the next reset, any write operations to this register will be ignored by the system.

English manual:

2.  If the key available on the data bus is incorrect, the FLASH_PUKR register remains 
locked until the next reset. Any new write commands sent to this address are 
discarded. 

4.  If the key available on the data bus is incorrect, the data EEPROM area remains write 
protected until the next reset. Any new write command sent to this address is ignored.

These instructions give the impression that if the first key is entered incorrectly, you can repeat it until it is unlocked, but if the first key is entered correctly and the second key is entered incorrectly, it will be permanently locked and any write operations to the register will be ignored until the next unlock after reset.

In fact, after experiments, I found that no matter the first key or the second key is wrong, I can repeat the operation until it is unlocked.