STM32L552CET6PTR datasheet(23/340 Pages) STMICROELECTRONICS

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DS12737 Rev 6

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STM32L552xx

Functional overview

For example, a software code in the secure Flash memory hidden protection area can

be executed only once and deny any further access to this area until next system reset.

•

Volatile block-based secure Flash area. In a block-based secure area, each page can

be programmed on-the-fly as secure or non-secure.

3.5

Embedded SRAM

The devices feature 256 Kbytes of embedded SRAM. This SRAM is split into three blocks:

•

192 Kbytes mapped at address 0x2000 0000 (SRAM1).

•

64 Kbytes located at address 0x0A03 0000 with hardware parity check (SRAM2).

This memory is also mapped at address 0x2003 0000 offering a contiguous address

space with the SRAM1.

This block is accessed through the C-bus for maximum performance. Either 64 Kbytes

or upper 4 Kbytes of SRAM2 can be retained in Standby mode.

The SRAM2 can be write-protected with 1 Kbyte granularity.

The memory can be accessed in read/write at CPU clock speed with 0 wait states.

TrustZone security

When the TrustZone security is enabled, all SRAMs are secure after reset. The SRAM can

be programmed as non-secure by block based using the MPCBB (memory protection

controller block based) in GTZC controller. The granularity of SRAM secure block based is a

page of 256 bytes.

3.6

Boot modes

At startup, a BOOT0 pin, nBOOT0 and NSBOOTADDx[24:0] / SECBOOTADD0[24:0] option

bytes are used to select the boot memory address which includes:

•

Boot from any address in user Flash

•

Boot from system memory bootloader

•

Boot from any address in embedded SRAM

•

Boot from Root Security service (RSS)

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.

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

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

firmware upgrade).

The bootloader is available on all devices. Refer to the application note STM32

microcontroller system memory boot mode (AN2606) for more details.

The root secure services (RSS) are embedded in a Flash memory area named secure

information block, programmed during ST production.

The RSS enables for example the secure firmware installation (SFI) thanks to the RSS

extension firmware (RSSe SFI).

This feature allows the customers to protect the confidentiality of the firmware to be

provisioned into the STM32 device when the production is subcontracted to a third party.

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