Pwm Input Mode (Only For Tim15); Figure 170. Pwm Input Mode Timing - STMicroelectronics STM32F05 series Reference Manual

RM0091
Note: IC interrupt and/or DMA requests can be generated by software by setting the
corresponding CCxG bit in the TIMx_EGR register.
18.4.7

PWM input mode (only for TIM15)

This mode is a particular case of input capture mode. The procedure is the same except:
●
Two ICx signals are mapped on the same TIx input.
● These 2 ICx signals are active on edges with opposite polarity.
●
One of the two TIxFP signals is selected as trigger input and the slave mode controller
is configured in reset mode.
For example, you can measure the period (in TIMx_CCR1 register) and the duty cycle (in
TIMx_CCR2 register) of the PWM applied on TI1 using the following procedure (depending
on CK_INT frequency and prescaler value):
●
Select the active input for TIMx_CCR1: write the CC1S bits to 01 in the TIMx_CCMR1
register (TI1 selected).
● Select the active polarity for TI1FP1 (used both for capture in TIMx_CCR1 and counter
clear): write the CC1P bit to '0' (active on rising edge).
●
Select the active input for TIMx_CCR2: write the CC2S bits to 10 in the TIMx_CCMR1
register (TI1 selected).
●
Select the active polarity for TI1FP2 (used for capture in TIMx_CCR2): write the CC2P
bit to '1' (active on falling edge).
● Select the valid trigger input: write the TS bits to 101 in the TIMx_SMCR register
(TI1FP1 selected).
●
Configure the slave mode controller in reset mode: write the SMS bits to 100 in the
TIMx_SMCR register.
●
Enable the captures: write the CC1E and CC2E bits to '1' in the TIMx_CCER register.

Figure 170. PWM input mode timing

TIMx_CNT
TIMx_CCR1
TIMx_CCR2
1. The PWM input mode can be used only with the TIMx_CH1/TIMx_CH2 signals due to the fact that only
TI1FP1 and TI2FP2 are connected to the slave mode controller.
TI1
0004 0000
IC1 capture
IC2 capture
reset counter
Doc ID 018940 Rev 1
General-purpose timers (TIM15/16/17)
0001 0002 0003
0004
0002
0004 0000
IC2 capture IC1 capture
pulse width period
measurement measurement
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