STMicroelectronics STM32L476 User Manual

UM1879 Rev 4 9/41
UM1879 Bootloader limitations
40
9 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, I
2
C bus, USB
or CAN.
Bootloader version can be identified by reading the Bootloader ID at the address
0x1FFF6FFE.
The STM32L476VGT6 part soldered on the 32L476GDISCOVERY main board is marked
with a date code corresponding to its date of manufacturing. STM32L476VGT6 parts with
the date code prior or equal to week 22 of 2015 are fitted with bootloader V
9.0 affected by
the limitations to be worked around, as described hereunder. Parts with the date code
starting from week 23 of 2015 contain bootloader V
9.2 in which the limitations no longer
exist.
To locate the visual date code information on the STM32L476VGT6 package, refer to its
datasheet (DS10198) 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 23 of 2015 bares the
date code 5
23.
Bootloader ID of the bootloader V 9.0 is 0x90.
The following limitations exist in the bootloader V 9.0:
1. RAM data get corrupted when written via USART/SPI/I
2
C/USB interface
Description:
Data write operation into RAM space via USART, SPI, I
2
C bus or USB results in wrong
or no data written.
Workaround:
To correct the issue of wrong write into RAM, download the STSW-STM32158
bootloader V
9.0 patch package from the www.st.com website and load "Bootloader
V9.0 SRAM patch" to the MCU, following the information in readme.txt file available in
the package.
2. User Flash memory data get corrupted when written via CAN interface
Description:
Data write operation into user Flash memory space via CAN interface results in wrong
or no data written.
Workaround:
To correct the issue of wrong write into Flash memory, download the STSW-STM32158
bootloader V
0.9 patch package from the www.st.com website and load "Bootloader V9.0
CAN patch" to the MCU, following the information in readme.txt file available in the package.

STMicroelectronics STM32L476 Specifications

General

Brand	STMicroelectronics
Model	STM32L476
Category	Motherboard
Language	English