ST STM32L4 5 Series Reference Manual page 103

RM0351
automatically when PG bit is set, and disabled automatically when PG bit is cleared, except
if the HSI16 is previously enabled with HSION in RCC_CR register.
If the user needs to program only one word, double word must be completed with the erase
value 0xFFFF FFFF to launch automatically the programming.
ECC is calculated from the double word to program.
Fast programming
This mode allows to program a row (32 double word) and to reduce the page programming
time by eliminating the need for verifying the flash locations before they are programmed
and to avoid rising and falling time of high voltage for each double word. During fast
programming, the CPU clock frequency (HCLK) must be at least 8 MHz.
Only the main memory can be programmed in Fast programming mode.
The Flash main memory programming sequence in standard mode is as follows:
1. Perform a mass erase of the bank to program. If not, PGSERR is set.
2. Check that no Flash main memory operation is ongoing by checking the BSY bit in the
Flash status register
3. Check and clear all error programming flag due to a previous programming.
4. Set the FSTPG bit in
5. Write the 32 double words to program a row. Only double words can be programmed:
–
–
6. Wait until the BSY bit is cleared in the FLASH_SR register.
7. Check that EOP flag is set in the FLASH_SR register (meaning that the programming
operation has succeed), and clear it by software.
8. Clear the FSTPG bit in the FLASH_SR register if there no more programming request
anymore.
Note: If the flash is attempted to be written in Fast programming mode while a read operation is on
going in the same bank, the programming is aborted without any system notification (no
error flag is set).
When the Flash interface has received the first double word, programming is automatically
launched. The BSY bit is set when the high voltage is applied for the first double word, and it
is cleared when the last double word has been programmed or in case of error. The internal
oscillator HSI16 (16 MHz) is enabled automatically when FSTPG bit is set, and disabled
automatically when FSTPG bit is cleared, except if the HSI16 is previously enabled with
HSION in RCC_CR register.
The 32 double word must be written successively. The high voltage is kept on the flash for
all the programming. Maximum time between two double words write requests is the time
programming (around 20us). If a second double word arrives after this time programming,
fast programming is interrupted and MISSERR is set.
High voltage mustn't exceed 8 ms for a full row between 2 erases. This is guaranteed by the
sequence of 32 double words successively written with a clock system greater or equal to
8MHz. An internal time-out counter counts 7ms when Fast programming is set and stops the
programming when time-out is over. In this case the FASTERR bit is set.
If an error occurs, high voltage is stopped and next double word to programmed is not
programmed. Anyway, all previous double words have been properly programmed.
(FLASH_SR).
Flash control register
Write a first word in an address aligned with double word
Write the second word.
DocID024597 Rev 5
Embedded Flash memory (FLASH)
(FLASH_CR).
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