STM32F048T6 datasheet(13/98 Pages) STMICROELECTRONICS

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STM32F048C6 STM32F048G6 STM32F048T6

Functional overview

3.4

Cyclic redundancy check calculation unit (CRC)

The CRC (cyclic redundancy check) calculation unit is used to get a CRC code from a 32-bit

data word and a CRC-32 (Ethernet) polynomial.

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.

3.5

Power management

3.5.1

Power supply schemes

•

VDD = VDDIO1 = 1.8 V ± 8%: external power supply for I/Os (VDDIO1) and digital logic. It

is provided externally through VDD pins.

•

VDDA = from VDD to 3.6 V: external analog power supply for ADC, RCs and PLL

(minimum voltage to be applied to VDDA is 2.4 V when the ADC is used). It is provided

externally through VDDA pin. The VDDA voltage level must be always greater or equal

to the VDD voltage level and must be established first.

•

VDDIO2 = 1.65 to 3.6 V: external power supply for marked I/Os. VDDIO2 is provided

externally through the VDDIO2 pin. The VDDIO2 voltage level is completely independent

from VDD or VDDA, but it must not be provided without a valid supply on VDD. The

VDDIO2 supply is monitored and compared with the internal reference voltage

(VREFINT). When the VDDIO2 is below this threshold, all the I/Os supplied from this rail

are disabled by hardware. The output of this comparator is connected to EXTI line 31

and it can be used to generate an interrupt. Refer to the pinout diagrams or tables for

concerned I/Os list.

•

VBAT = 1.65 to 3.6 V: power supply for RTC, external clock 32 kHz oscillator and

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

For more details on how to connect power pins, refer to Figure 9: Power supply scheme.

3.5.2

Power-on reset

To guarantee a proper power-on reset, the NPOR pin must be held low until VDD is stable.

When VDD is stable, the reset state can be exited either by:

•

putting the NPOR pin in high impedance (NPOR pin has an internal pull-up), or by

•

forcing the pin to high level by connecting it to VDDA

3.5.3

Low-power modes

The STM32F048x6 microcontrollers support two low-power modes to achieve the best

compromise between low power consumption, short startup time and available wakeup

sources:

•

Sleep mode

In Sleep mode, only the CPU is stopped. All peripherals continue to operate and can

wake up the CPU when an interrupt/event occurs.

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