Advanced-control timers (TIM1/TIM8/TIM20) RM0440
1114/2126 RM0440 Rev 4
been detected (sampled at f
DTS
frequency). Then write IC1F bits to 0011 in the
TIMx_CCMR1 register.
• Select the edge of the active transition on the tim_ti1 channel by writing CC1P and
CC1NP bits to 0 in the TIMx_CCER register (rising edge in this case).
• Program the input prescaler. In our example, we wish the capture to be performed at
each valid transition, so the prescaler is disabled (write IC1PS bits to ‘00’ in the
TIMx_CCMR1 register).
• Enable capture from the counter into the capture register by setting the CC1E bit in the
TIMx_CCER register.
• If needed, enable the related interrupt request by setting the CC1IE bit in the
TIMx_DIER register, and/or the DMA request by setting the CC1DE bit in the
TIMx_DIER register.
When an input capture occurs:
• The TIMx_CCR1 register gets the value of the counter on the active transition.
• CC1IF flag is set (interrupt flag). CC1OF is also set if at least two consecutive captures
occurred whereas the flag was not cleared.
• An interrupt is generated depending on the CC1IE bit.
• A DMA request is generated depending on the CC1DE bit.
In order to handle the overcapture, it is recommended to read the data before the
overcapture flag. This is to avoid missing an overcapture which could happen after reading
the flag and before reading the data.
Note: IC interrupt and/or DMA requests can be generated by software by setting the
corresponding CCxG bit in the TIMx_EGR register.
28.3.10 PWM input mode
This mode allows to measure both the period and the duty cycle of a PWM signal connected
to single tim_tix input:
• The TIMx_CCR1 register holds the period value (interval between two consecutive
rising edges)
• The TIM_CCR2 register holds the pulsewidth (interval between two consecutive rising
and falling edges
This mode is a particular case of input capture mode. The set-up procedure is similar with
the following differences:
• Two ICx signals are mapped on the same tim_tixfp1 input.
• These 2 ICx signals are active on edges with opposite polarity.
• One of the two tim_tixfp signals is selected as trigger input and the slave mode
controller is configured in reset mode.
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