RM0385 Datasheet, PDF (79/1644 Pages) STMicroelectronics – This reference manual targets application developers

RM0385
Embedded Flash memory (FLASH)
3.3.6
Note:
3.3.7
Note:
Flash erase sequences
The Flash memory erase operation can be performed at sector level or on the whole Flash
memory (Mass Erase). Mass Erase does not affect the OTP sector or the configuration
sector.
Sector Erase
To erase a sector, follow the procedure below:
1. Check that no Flash memory operation is ongoing by checking the BSY bit in the
FLASH_SR register
2. Set the SER bit and select the sector out of the 8 in the main memory block) you wish
to erase (SNB) in the FLASH_CR register
3. Set the STRT bit in the FLASH_CR register
4. Wait for the BSY bit to be cleared
Mass Erase
To perform Mass Erase, the following sequence is recommended:
1. Check that no Flash memory operation is ongoing by checking the BSY bit in the
FLASH_SR register
2. Set the MER bit in the FLASH_CR register
3. Set the STRT bit in the FLASH_CR register
4. Wait for the BSY bit to be cleared
If MERx and SER bits are both set in the FLASH_CR register, mass erase is performed.
If both MERx and SER bits are reset and the STRT bit is set, an unpredictable behavior may
occur without generating any error flag. This condition should be forbidden.
Flash programming sequences
Standard programming
The Flash memory programming sequence is as follows:
1. Check that no main Flash memory operation is ongoing by checking the BSY bit in the
FLASH_SR register.
2. Set the PG bit in the FLASH_CR register
3. Perform the data write operation(s) to the desired memory address (inside main
memory block or OTP area):
– Byte access in case of x8 parallelism
– Half-word access in case of x16 parallelism
– Word access in case of x32 parallelism
– Double word access in case of x64 parallelism
4. Wait for the BSY bit to be cleared.
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.
If an erase and a program operation are requested simultaneously, the erase operation is
performed first.
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