EM357-RTR datasheet(128/241 Pages) SILABS

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To detect missed captures reliably, read captured data in TIMxCCRy before checking the missed capture/compare

flag. This sequence avoids missing a capture that could happen after reading the flag and before reading the data.

Note:

Software can generate IC interrupt requests by setting the corresponding TIM_CCyG bit in the TIMx_EGR register.

9.3.6. PWM Input Mode

This mode is a particular case of input capture mode. The procedure is the same except:



Two ICy signals are mapped on the same TIy input.



These two ICy signals are active on edges with opposite polarity.



One of the two TIyFP signals is selected as trigger input and the slave mode controller is configured in

reset mode.

For example, to measure the period in the TIMx_CCR1 register and the duty cycle in the TIMx_CCR2 register of

the PWM applied on TI1, use the following procedure depending on CK_INT frequency and prescaler value:



Select the active input for TIMx_CCR1: write the TIM_CC1S bits to 01 in the TIMx_CCMR1 register (TI1

selected).



Select the active polarity for TI1FP1, used both for capture in the TIMx_CCR1 and counter clear, by writing

the TIM_CC1P bit to 0 (active on rising edge).



Select the active input for TIMx_CCR2by writing the TIM_CC2S bits to 10 in the TIMx_CCMR1 register

(TI1 selected).



Select the active polarity for TI1FP2 (used for capture in the TIMx_CCR2) by writing the TIM_CC2P bit to 1

(active on falling edge).



Select the valid trigger input by writing the TIM_TS bits to 101 in the TIMx_SMCR register (TI1FP1

selected).



Configure the slave mode controller in reset mode by writing the TIM_SMS bits to 100 in the TIMx_SMCR



Enable the captures by writing the TIM_CC1E and TIM_CC2E bits to 1 in the TIMx_CCER register.

Figure 9.20 illustrates this example.

Figure 9.20. PWM Input Mode Timing

EM357-RTR Datasheet(PDF) 128 Page - Silicon Laboratories