GD32F3x0 User Manual
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Result: when you wanted input signal is got, TIMERx_CHxCV will be set by counter’s value.
And CHxIF is asserted. If the CHxIF is high, the CHxOF will be asserted also. The interrupt
and DMA request will be asserted based on the configuration of CHxIE and CHxDEN in
TIMERx_DMAINTEN.
Direct generation: if you want to generate a DMA request or Interrupt, you can set CHxG by
software directly.
The channel input capture function can be also used for pulse width measurement from
signals on the TIMERx_CHx pins. For example, PWM signal connect to CI0 input. Select
channel 0 capture signals to CI0 by setting CH0MS to 2’b01 in the channel control register
(TIMERx_CHCTL0) and set capture on rising edge. Select channel 1 capture signal to CI0
by setting CH1MS to 2’b10 in the channel control register (TIMERx_CHCTL0) and set
capture on falling edge. The counter set to restart mode and restart on channel 0 rising edge.
Then the TIMERX_CH0CV can measure the PWM period and the TIMERx_CH1CV can
measure the PWM duty.
Channel output compare function
In channel output compare function, the TIMERx can generate timed pulses with
programmable position, polarity, duration and frequency. When the counter matches the
value in the CHxVAL register of an output compare channel, the channel (n) output can be
set, cleared, or toggled based on CHxCOMCTL. When the counter reaches the value in the
CHxVAL register, the CHxIF bit is set and the channel (n) interrupt is generated if CHxIE = 1.
And the DMA request will be asserted, if CHxDEN=1.
So, the process can be divided to several steps as below:
Step1: Clock Configuration. Such as clock source, clock prescaler and so on.
Step2: Compare mode configuration.
* Set the shadow enable mode by CHxCOMSEN
* Set the output mode (Set/Clear/Toggle) by CHxCOMCTL.
* Select the active high polarity by CHxP/CHxNP
* Enable the output by CHxEN
Step3: Interrupt/DMA-request enables configuration by CHxIE/ CHxDEN
Step4: Compare output timing configuration by TIMERx_CAR and TIMERx_CHxCV
About the CHxVAL; you can change it on the go to meet the waveform you expected.
Step5: Start the counter by CEN.
The timechart below show the three compare modes toggle/set/clear. CAR=0x63,
CHxVAL=0x3.
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