RM0440 Rev 4 155/2126
RM0440 Embedded Flash memory (FLASH) for category 4 devices
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1. Check that no Flash memory operation is ongoing by checking the BSY bit in the
FLASH_SR register.
2. Check and clear all error programming flags due to a previous programming. If not,
PGSERR is set.
3. Set the MER1 bit in the Flash control register (FLASH_CR).
4. Set the STRT bit in the FLACH_CR register.
5. Wait for the BSY bit to be cleared in the Flash status register (FLASH_SR).
Note: The internal oscillator HSI16 (16 MHz) is enabled automatically when STRT bit is set, and
disabled automatically when STRT bit is cleared, except if the HSI16 is previously enabled
with HSION in RCC_CR register.
If the Flasb memory contains a write-protected area (by WRP or PCROP), WRPERR is set
and the mass erase request is aborted.
4.3.7 Flash main memory programming sequences
The Flash memory is programmed 72 bits at a time (64 bits + 8 bits ECC).
Programming in a previously programmed address is not allowed except if the data to write
is full zero, and any attempt sets PROGERR flag in the Flash status register (FLASH_SR).
It is only possible to program double word (2 x 32-bit data).
• Any attempt to write byte or half-word sets SIZERR flag in the FLASH_SR register.
• Any attempt to write a double word which is not aligned with a double word address
sets PGAERR flag in the FLASH_SR register.
Standard programming
The Flash memory programming sequence in standard mode is as follows:
1. Check that no Flash main memory operation is ongoing by checking the BSY bit in the
Flash status register (FLASH_SR).
2. Check and clear all error programming flags due to a previous programming. If not,
PGSERR is set.
3. Set the PG bit in the Flash control register (FLASH_CR).
4. Perform the data write operation at the desired memory address, inside main memory
block or OTP area. Only double word can be programmed.
– Write a first word in an address aligned with double word
– Write the second word
5. Wait until the BSY bit is cleared in the FLASH_SR register.
6. Check that EOP flag is set in the FLASH_SR register (meaning that the programming
operation has succeed), and clear it by software.
7. Clear the PG bit in the FLASH_SR register if there no more programming request
anymore.
Note: When the flash interface has received a good sequence (a double word), programming is
automatically launched and BSY bit is set. The internal oscillator HSI16 (16 MHz) is enabled
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