Схемы, платы, компоненты

У STM32F030 прямо сказано следующее: 

The Flash memory interface preliminarily reads the value at the addressed main Flash memory location and checks that it has been erased. If not, the program operation is skipped and a warning is issued by the PGERR bit in FLASH_SR register. The only exception to this is when 0x0000 is programmed. In this case, the location is correctly programmed to 0x0000 and the PGERR bit is not set.

У STM32F103 сказано то же самое:

FPEC preliminarily reads the value at the addressed main Flash memory location and checks that it has been erased. If not, the program operation is skipped and a warning is issued by the PGERR bit in FLASH_SR register (the only exception to this is when 0x0000 is programmed. In this case, the location is correctly programmed to 0x0000 and the PGERR bit is not set).

У STM32F407 сказано совсем другое:

Note: Successive write operations are possible without the need of an erase operation when changing bits from ‘1’ to ‘0’. Writing ‘1’ requires a Flash memory erase operation.