STM32L021D4 datasheet(27/114 Pages) STMICROELECTRONICS

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STM32L021x4

Functional overview

3.12

Ultra-low-power comparators and reference voltage

The STM32L021x4 embed two comparators sharing the same current bias and reference

voltage. The reference voltage can be internal or external (coming from an I/O).

•

One comparator with ultra low consumption

•

One comparator with rail-to-rail inputs, fast or slow mode.

•

The threshold can be one of the following:

–

External I/O pins

–

Internal reference voltage (VREFINT)

–

submultiple of Internal reference voltage(1/4, 1/2, 3/4) for the rail to rail

comparator.

Both comparators can wake up the devices from Stop mode, and be combined into a

window comparator.

The internal reference voltage is available externally via a low-power / low-current output

buffer (driving current capability of 1 µA typical).

3.13

System configuration controller

The system configuration controller provides the capability to remap some alternate

functions on different I/O ports.

The highly flexible routing interface allows the application firmware to control the routing of

different I/Os to the TIM2, TIM21 and LPTIM1 timer input captures. It also controls the

routing of internal analog signals to the ADC, COMP1 and COMP2 and the internal

reference voltage VREFINT.

3.14

AES

The AES Hardware Accelerator can be used to encrypt and decrypt data using the AES

algorithm (compatible with FIPS PUB 197, 2001 Nov 26):

•

Key scheduler

•

Key derivation for decryption

•

128-bit data block processed

•

128-bit key length

•

213 clock cycles to encrypt/decrypt one 128-bit block

•

Electronic codebook (ECB), cypher block chaining (CBC), and counter mode (CTR)

supported by hardware.

The AES can be served by the DMA controller.

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