Bootloader Limitations; Table 5. Boot Selection Switch - ST STM32L4R9I-EVAL User Manual

Hardware layout and configuration
The boot option is configured by setting switch SW1 (BOOT) and the boot base address
programmed in the nBOOT1, nBOOT0 and nSWBOOT0 of FLASH_OPTR option bytes.
Switch
SW1
9.8.1

Bootloader limitations

Boot from system Flash memory results in executing bootloader code stored in the system
Flash memory protected against writing and erasing. This allows in-system programming
(ISP), that is, flashing the STM32 user Flash memory. It also allows writing data into RAM.
The data come in via one of communication interfaces such as USART, SPI, I2C bus, USB
or CAN.
Bootloader version is identified by reading the Bootloader ID at the address 0x1FFF6FFE:
the content is 0x91 for bootloader V9.1 and 0x92 for V9.2.
The STM32L4R9AII6 part soldered on the STM32L4R9I-EVAL main board is marked with a
date code corresponding to its date of manufacturing. STM32L4R9AII6 parts with a date
code prior or equal to week 37 of 2017 are fitted with bootloader V9.1 affected by the
limitations to be worked around, as described hereunder. Parts with the date code starting
from week 38 of 2017 contain bootloader V9.2 in which the limitations no longer exist.
To locate the visual date code information on the STM32L4R9II6 package, refer to its
datasheet (DS12023) available at www.st.com, section Package Information. Date code
related portion of the package marking takes Y WW format, where Y is the last digit of the
year and WW is the week. For example, a part manufactured in week 38 of 2017 bares the
date code 7 38.
There is also another mean to identify the need for workaround: before opening the blister of
the Discovery Kit, just check the back side of the blister. At the bottom left side, if the
reference number is equal or higher than 32L4R9IDISCO/ 02-0, it means the bootloader
version is V9.2 and there is no need to apply workaround. Any other inferior number like
01-0 will need the workaround.
Bootloader ID for the bootloader V9.1 is 0x91.
The following limitation exists in the bootloader V9.1:
Some user Flash memory data get corrupted when written via SPI interface
Description:
During bootloader SPI Write Flash operation, some random 64-bits (2 double-words) may
be left blank at 0xFF
Workarounds:
24/87

Table 5. Boot selection switch

Setting
Default setting.
BOOT0 line is tied low. STM32L4R9AII6 boots from main Flash
memory or system memory.
BOOT0 line is tied high. STM32L4R9AII6 boots from system Flash
memory (nBOOT1 bit of FLASH_OPTR register is set high) or from
RAM (nBOOT1 is set low).
DocID030791 Rev 2
Description
UM2248