STM32WB09XE datasheet(14/73 Pages) STMICROELECTRONICS

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3.9

Reset management

The STM3WB09xE offers two different resets:

•

The PORESETn: this reset is provided by the low-power management unit (LPMU) analog block and

corresponds to a POR or PDR root cause. It is linked to power voltage ramp-up or ramp-down. This reset

impacts all resources of the STM3WB09xE. The exit from Shutdown mode is equivalent to a POR and thus

generates a PORESETn. The PORESETn signal is active when the power supply of the device is below a

threshold value or when the regulator does not provide the target voltage.

•

The PADRESETn (system reset): this reset is built through several sources:

–

PORESETn

–

Reset due to the watchdog

The STM3WB09xE device embeds a watchdog timer, which may be used to recover from software

crashes

–

Reset due to CPU Lockup

The Cortex®-M0+ generates a lockup to indicate the core is in the lock-up state resulting from an

unrecoverable exception. The lock-up reset is masked if a debugger is connected to the Cortex®-

M0+

–

Software system reset

The system reset request is generated by the debug circuitry of the Cortex®-M0+. The debugger sets

the SYSRESETREQ bit of the application interrupt and reset control register (AIRCR). This system

reset request through the AIRCR can also be done by the embedded software (into the hardfault

handler for instance)

–

Reset from the RSTN external pin

The RSTN pin toggles to inform that a reset has occurred

This PADRESETn resets all resources of the STM3WB09xE, except:

•

Debug features

•

Flash controller key management

•

RTC timer

•

Power controller unit

•

Part of the RCC registers

The pulse generator guarantees a minimum reset pulse duration of 20 μs for each internal reset source. In case

of reset from the RSTN external pad, the reset pulse is generated when the pad is asserted low.

3.10

Operating modes

Several operating modes are defined for the STM3WB09xE:

•

Run mode

•

Deepstop mode

•

Shutdown mode

Table 4. Relationship between the low-power modes and functional blocks

Mode

Shutdown

Deepstop

Idle

Run

CPU

OFF

Flash

OFF

RAM

OFF

ON/OFF granularity 12

Kbytes

ON/OFF

Radio

OFF

ON/OFF

Supply system

OFF

ON ( DC-DC ON/

OFF)

ON ( DC-DC ON/

OFF)

OFF

HS clock

OFF

LS clock

OFF

ON/OFF

STM32WB09xE

Functional overview

DS14210 - Rev 6

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