STM32L431 datasheet(19/200 Pages) STMICROELECTRONICS

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STM32L431xx

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 and CAN 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.

•

VDDA = 1.62 V (ADCs/COMPs) / 1.8 (DACs/OPAMP) to 3.6 V: external analog power

supply for ADCs, DACs, OPAMP, Comparators and Voltage reference buffer. The VDDA

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.

Note:

If these supplies are tied to ground, the I/Os supplied by these power supplies are not 5 V

tolerant (refer to Table 18: Voltage characteristics).

Note:

VDDIOx is the I/Os general purpose digital functions supply. VDDIOx represents VDDIO1, with

VDDIO1 = VDD.

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