Cyclic Redundancy Check Calculation Unit (Crc); Power Management; Power Supply Schemes; Power Supply Supervisors - STMicroelectronics STM32F031F4 Manual

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STM32F031x4 STM32F031x6
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


V
DD
regulator. It is provided externally through VDD pins.

V
DDA
and PLL (minimum voltage to be applied to V
provided externally through VDDA pin. The V
or equal to the V

V
BAT
backup registers (through power switch) when V
For more details on how to connect power pins, refer to
3.5.2

Power supply supervisors

The device has integrated power-on reset (POR) and power-down reset (PDR) circuits.
They are always active, and ensure proper operation above a threshold of 2 V. The device
remains in reset mode when the monitored supply voltage is below a specified threshold,
V
POR/PDR

The POR monitors only the V
that V

The PDR monitors both the V
supply supervisor can be disabled (by programming a dedicated Option bit) to reduce
the power consumption if the application design ensures that V
equal to V
The device features an embedded programmable voltage detector (PVD) that monitors the
V power supply and compares it to the V
DD
when V
DD
threshold. The interrupt service routine can then generate a warning message and/or put
the MCU into a safe state. The PVD is enabled by software.
3.5.3

Voltage regulator

The regulator has two operating modes and it is always enabled after reset.

Main (MR) is used in normal operating mode (Run).

Low power (LPR) can be used in Stop mode where the power demand is reduced.
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= V = 2.0 to 3.6 V: external power supply for I/Os (V
DDIO1
= from V to 3.6 V: external analog power supply for ADC, Reset blocks, RCs
DD
voltage level and must be established first.
DD
= 1.65 to 3.6 V: power supply for RTC, external clock 32 kHz oscillator and
, without the need for an external reset circuit.
should arrive first and be greater than or equal to V
DDA
.
DD
drops below the V
PVD
DocID025743 Rev 3
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is 2.4 V when the ADC is used). It is
DDA
voltage level must be always greater
DDA
DD
supply voltage. During the startup phase it is required
DD
and V supply voltages, however the V
DD DDA
threshold. An interrupt can be generated
PVD
threshold and/or when V
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Functional overview
) and the internal
DDIO1
is not present.
Figure 12: Power supply
.
DD
is higher than or
DDA
is higher than the V
DD
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scheme.
power
DDA
PVD
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