STM32L021D4 datasheet(28/114 Pages) STMICROELECTRONICS

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Functional overview

STM32L021x4

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DocID027982 Rev 5

3.15

Timers and watchdogs

The ultra-low-power STM32L021x4 devices include two general-purpose timers, one low-

power timer (LPTIM1), two watchdog timers and the SysTick timer.

Table 6 compares the features of the general-purpose and basic timers.

3.15.1

General-purpose timers (TIM2, TIM21)

There are three synchronizable general-purpose timers embedded in the STM32L021x4

devices (see Table 6 for differences).

TIM2

TIM2 is based on 16-bit auto-reload up/down counter. It includes a 16-bit prescaler. It

features four independent channels each for input capture/output compare, PWM or one-

pulse mode output.

The TIM2 general-purpose timers can work together or with the TIM21 general-purpose

timer via the Timer Link feature for synchronization or event chaining. Its counter can be

frozen in debug mode. Any of the general-purpose timers can be used to generate PWM

outputs.

TIM2 has independent DMA request generation.

This timer is capable of handling quadrature (incremental) encoder signals and the digital

outputs from 1 to 3 hall-effect sensors.

TIM21

TIM21 is based on a 16-bit auto-reload up/down counter. It includes a 16-bit prescaler. It has

two independent channels for input capture/output compare, PWM or one-pulse mode

output. It can work together and be synchronized with TIM2 full-featured general-purpose

timer.

It can also be used as simple timebase and be clocked by the LSE clock source

(32.768 kHz) to provide independent timebase from the main CPU clock.

Table 6. Timer feature comparison

Timer

Counter

resolution

Counter type

Prescaler factor

DMA

request

generation

Capture/compare

channels

Complementary

outputs

TIM2

16-bit

Up, down,

up/down

Any integer between

1 and 65536

Yes

TIM21

16-bit

Up, down,

up/down

Any integer between

1 and 65536

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