STM32W108HB datasheet(12/179 Pages) STMICROELECTRONICS

12 / 179 page

Description

STM32W108CB, STM32W108HB

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Doc ID 16252 Rev 2

pulse width shorter than the Internal APB2 clock period. Up to 80 GPIOs can be connected

to the 16 external interrupt lines.

1.2.6

Clocks and startup

System clock selection is performed on startup, however the internal RC 8 MHz oscillator is

selected as default CPU clock on reset. An external 4-16 MHz clock can be selected, in

which case it is monitored for failure. If failure is detected, the system automatically switches

back to the internal RC oscillator. A software interrupt is generated if enabled. Similarly, full

interrupt management of the PLL clock entry is available when necessary (for example on

failure of an indirectly used external crystal, resonator or oscillator).

Several prescalers allow the configuration of the AHB frequency, the high-speed APB

(APB2) and the low-speed APB (APB1) domains. The maximum frequency of the AHB and

the APB domains is 20 MHz.

1.2.7

Boot modes

At startup, boot pins are used to select one of three boot options:

●

Boot from User Flash

●

Boot from System memory

●

Boot from embedded SRAM

The boot loader is located in System memory. It is used to reprogram the Flash memory by

using USART1. For further details please refer to AN2606.

1.2.8

Power supply schemes

●

VDD = 2.0 to 3.6 V: External power supply for I/Os and the internal regulator. Provided

externally through VDD pins.

●

VSSA, VDDA = 2.0 to 3.6 V: External analog power supplies for ADC, Reset blocks, RCs

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

VDDA and VSSA must be connected to VDD and VSS, respectively.

●

VBAT = 1.8 to 3.6 V: Power supply for RTC, external clock 32 kHz oscillator and backup

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

1.2.9

Power supply supervisor

The device has an integrated power on reset (POR)/power down reset (PDR) circuitry. It is

always active, and ensures proper operation starting from/down to 2 V. The device remains

in reset mode when VDD is below a specified threshold, VPOR/PDR, without the need for

an external reset circuit.

The device features an embedded programmable voltage detector (PVD) that monitors the

VDD/VDDA power supply and compares it to the VPVD threshold. An interrupt can be

generated when VDD/VDDA drops below the VPVD threshold and/or when VDD/VDDA is

higher than the VPVD 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.

STM32W108HB Datasheet(PDF) 12 Page - STMicroelectronics

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