Figure 169. Example Of Encoder Interface Mode With Ti1Fp1 Polarity Inverted; Timer Input Xor Function - STMicroelectronics STM32F405 Reference Manual

RM0090
Figure 169
configuration as above except CC1P=1).

Figure 169. Example of encoder interface mode with TI1FP1 polarity inverted

Counter
The timer, when configured in Encoder Interface mode provides information on the sensor's
current position. You can obtain dynamic information (speed, acceleration, deceleration) by
measuring the period between two encoder events using a second timer configured in
capture mode. The output of the encoder which indicates the mechanical zero can be used
for this purpose. Depending on the time between two events, the counter can also be read
at regular times. You can do this by latching the counter value into a third input capture
register if available (then the capture signal must be periodic and can be generated by
another timer). when available, it is also possible to read its value through a DMA request
generated by a Real-Time clock.
18.3.13

Timer input XOR function

The TI1S bit in the TIM_CR2 register, allows the input filter of channel 1 to be connected to
the output of a XOR gate, combining the three input pins TIMx_CH1 to TIMx_CH3.
The XOR output can be used with all the timer input functions such as trigger or input
capture.
18.3.14 Timers and external trigger synchronization
The TIMx Timers can be synchronized with an external trigger in several modes: Reset
mode, Gated mode and Trigger mode.
Slave mode: Reset mode
The counter and its prescaler can be reinitialized in response to an event on a trigger input.
Moreover, if the URS bit from the TIMx_CR1 register is low, an update event UEV is
generated. Then all the preloaded registers (TIMx_ARR, TIMx_CCRx) are updated.
In the following example, the upcounter is cleared in response to a rising edge on TI1 input:
•
Configure the channel 1 to detect rising edges on TI1. Configure the input filter duration
(in this example, we don't need any filter, so we keep IC1F=0000). The capture
prescaler is not used for triggering, so you don't need to configure it. The CC1S bits
select the input capture source only, CC1S = 01 in the TIMx_CCMR1 register. Write
gives an example of counter behavior when TI1FP1 polarity is inverted (same
forward jitter
TI1
TI2
down
DocID018909 Rev 11
General-purpose timers (TIM2 to TIM5)
backward jitter
up
forward
down
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