STM32L15XCC datasheet(23/136 Pages) STMICROELECTRONICS

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STM32L151xC STM32L152xC

Functional overview

3.5

Low-power real-time clock and backup registers

The real-time clock (RTC) is an independent BCD timer/counter. Dedicated registers contain

the sub-second, second, minute, hour (12/24 hour), week day, date, month, year, in BCD

(binary-coded decimal) format. Correction for 28, 29 (leap year), 30, and 31 day of the

month are made automatically. The RTC provides two programmable alarms and

programmable periodic interrupts with wakeup from Stop and Standby modes.

The programmable wakeup time ranges from 120 µs to 36 hours.

The RTC can be calibrated with an external 512 Hz output, and a digital compensation

circuit helps reduce drift due to crystal deviation.

The RTC can also be automatically corrected with a 50/60Hz stable powerline.

The RTC calendar can be updated on the fly down to sub second precision, which enables

network system synchronization.

A time stamp can record an external event occurrence, and generates an interrupt.

There are thirty-two 32-bit backup registers provided to store 128 bytes of user application

data. They are cleared in case of tamper detection.

Three pins can be used to detect tamper events. A change on one of these pins can reset

backup register and generate an interrupt. To prevent false tamper event, like ESD event,

these three tamper inputs can be digitally filtered.

3.6

GPIOs (general-purpose inputs/outputs)

Each of the GPIO pins can be configured by software as output (push-pull or open-drain), as

input (with or without pull-up or pull-down) or as peripheral alternate function. Most of the

GPIO pins are shared with digital or analog alternate functions, and can be individually

remapped using dedicated AFIO registers. All GPIOs are high current capable. The

alternate function configuration of I/Os can be locked if needed following a specific

sequence in order to avoid spurious writing to the I/O registers. The I/O controller is

connected to the AHB with a toggling speed of up to 16 MHz.

External interrupt/event controller (EXTI)

The external interrupt/event controller consists of 24 edge detector lines used to generate

interrupt/event requests. Each line can be individually configured to select the trigger event

(rising edge, falling edge, both) and can be masked independently. A pending register

maintains the status of the interrupt requests. The EXTI can detect an external line with a

pulse width shorter than the Internal APB2 clock period. Up to 83 GPIOs can be connected

to the 16 external interrupt lines. The 8 other lines are connected to RTC, PVD, USB,

comparator events or capacitive sensing acquisition.

STM32L15XCC Datenblatt(PDF) 23 Page - STMicroelectronics