STM32L4R9AI datasheet(22/306 Pages) STMICROELECTRONICS

22 / 306 page

Functional overview

STM32L4R5xx, STM32L4R7xx and STM32L4R9xx

22/306

DocID030321 Rev 3

The main features of the firewall are the following:

•

Three segments can be protected and defined thanks to the firewall registers:

–

Code segment (located in Flash or SRAM1 if defined as executable protected

area)

–

Non-volatile data segment (located in Flash)

–

Volatile data segment (located in SRAM1)

•

The start address and the length of each segment are configurable:

–

Code segment: up to 2048 Kbytes with granularity of 256 bytes

–

Non-volatile data segment: up to 2048 Kbytes with granularity of 256 bytes

–

Volatile data segment: up to 192 Kbytes of SRAM1 with a granularity of 64 bytes

•

Specific mechanism implemented to open the firewall to get access to the protected

areas (call gate entry sequence)

•

Volatile data segment can be shared or not with the non-protected code

•

Volatile data segment can be executed or not depending on the firewall configuration

The Flash readout protection must be set to level 2 in order to reach the expected level of

protection.

3.8

Boot modes

At startup, a BOOT0 pin and an nBOOT1 option bit are used to select one of three boot

options:

•

Boot from user Flash

•

Boot from system memory

•

Boot from embedded SRAM

The BOOT0 value may come from the PH3-BOOT0 pin or from an option bit depending on

the value of a user option bit to free the GPIO pad if needed.

A Flash empty-check mechanism is implemented to force the boot from system Flash if the

first Flash memory location is not programmed and if the boot selection is configured to boot

from main Flash.

The boot loader is located in the system memory. It is used to reprogram the Flash memory

by using USART, I2C, SPI, CAN or USB OTG FS in device mode through the DFU (device

firmware upgrade).

3.9

Cyclic redundancy check calculation unit (CRC)

The CRC (cyclic redundancy check) calculation unit is used to get a CRC code using a

configurable generator with polynomial value and size.

Among other applications, the CRC-based techniques are used to verify data transmission

or storage integrity. In the scope of the EN/IEC 60335-1 standard, they offer a mean to verify

the Flash memory integrity.

The CRC calculation unit helps to compute a signature of the software during runtime, which

can be ulteriorly compared with a reference signature generated at link-time and which can

be stored at a given memory location.

STM32L4R9AI Datasheet(PDF) 22 Page - STMicroelectronics

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