STM32L412RBI6PTR datasheet(19/192 Pages) STMICROELECTRONICS

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DS12469 Rev 4

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STM32L412xx

Functional overview

3.7

Boot modes

At startup, BOOT0 pin or nSWBOOT0 option bit, and BOOT1 option bit are used to select

one of three boot options:

•

Boot from user Flash

•

Boot from system memory

•

Boot from embedded SRAM

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 system memory. It is used to reprogram the Flash memory by

using USART, I2C, SPI or USB FS in Device mode through DFU (device firmware upgrade).

3.8

Cyclic redundancy check calculation unit (CRC)

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

configurable generator polynomial value and size.

Among other applications, 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 means of

verifying the Flash memory integrity. The CRC calculation unit helps compute a signature of

the software during runtime, to be compared with a reference signature generated at link-

time and stored at a given memory location.

3.9

Power supply management

3.9.1

Power supply schemes

•

VDD = 1.71 to 3.6 V: external power supply for I/Os (VDDIO1), the internal regulator and

the system analog such as reset, power management and internal clocks. It is provided

externally through VDD pins.

•

VDD12 = 1.00 to 1.32 V: external power supply bypassing internal regulator when

connected to an external SMPS. It is provided externally through VDD12 pins and only

available on packages with the external SMPS supply option. VDD12 does not require

any external decoupling capacitance and cannot support any external load.

•

VDDA = 1.62 V (ADC/COMP) / 1.8 (OPAMP) to 3.6 V: external analog power supply for

ADC, OPAMP, Comparator. The VDDA voltage level is independent from the VDD

voltage.

•

VDDUSB = 3.0 to 3.6 V: external independent power supply for USB transceivers. The

VDDUSB voltage level is independent from the VDD voltage.

•

VBAT = 1.55 to 3.6 V: power supply for RTC, external clock 32 kHz oscillator and

backup registers (through power switch) when VDD is not present.

Note:

When the functions supplied by VDDA are not used, this supply should preferably be shorted

to VDD.

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