General timer basic principle

1. References

       "STM32F1 Development Guide - Library Function Version" - Chapter 13, 14, 15  

       "STM32 Chinese Reference Manual V10" - Chapter 14 General Timer

2. Overview of General Timer

      STM32 timer

Differences between three STM32 timers

·General timer function features description

        The general TIMx (TIM2, TIM3, TIM4 and TIM5) timer features of STM32 include:

        Located on the low-speed APB1 bus (APB1)

        16-bit up, down, up/down (center-aligned) counting modes with auto-reload counter (TIMx_CNT).

        16-bit programmable (can be modified in real time) prescaler (TIMx_PSC), the counter clock frequency division factor is any value between 1 and 65535.

         4 independent channels (TIMx_CH1~4), which can be used as:

               ① Input capture

               ② Output comparison

               ③PWM generation (edge ​​or center aligned mode)

               ④Single pulse mode output

        · Synchronous circuits that can use external signals (TIMx_ETR) to control timers and timer interconnections (one timer can be used to control another timer).

        Generate interrupts/DMA on the following events (6 independent IRQ/DMA request generators):

           ① Update: counter overflow/underflow, counter initialization (by software or internal/external trigger)

           ②Trigger event (counter start, stop, initialization or internal/external trigger counting)

           ③ Input capture

           ④ Output comparison

           ⑤Support incremental (orthogonal) encoder and Hall sensor circuits for positioning

           ⑥Trigger input as external clock or cycle-by-cycle current management

      The general-purpose timer of STM32 can be used to measure the pulse length of the input signal (input capture) or generate output waveforms (output comparison and PWM), etc.

      ·Using the timer prescaler and RCC clock controller prescaler, the pulse length and waveform period can be adjusted from a few microseconds to a few milliseconds. Each general-purpose timer of STM32 is completely independent and does not share any resources with each other.  

      Counter mode

         The general timer can count up, count down, and count in both up and down bidirectional modes.

         ① Up counting mode: The counter starts counting down from the automatically loaded value (TIMx_ARR) to 0, then starts counting again from 0 and generates a counter overflow event.

         ② Down counting mode: The counter starts counting down from the automatically loaded value (TIMx_ARR) to 0, then restarts from the automatically loaded value and generates a counter underflow event.

         ③ Center-aligned mode (up/down counting): The counter starts counting from 0 to the automatically loaded value -1, generates a counter overflow event, then counts down to 1 and generates a counter

             Overflow event; then restart the count from 0.

      ·General timer working process

      Count clock selection

      Time base unit

      Update events

      ·Capture comparison array introduction

      Input capture mode

      PWM mode