Table 147. Counting Direction Versus Encoder Signals; Figure 241. Example Of Counter Operation In Encoder Interface Mode - ST STM32L4x6 Reference Manual

RM0351
Active edge
Counting on
TI1 only
Counting on
TI2 only
Counting on
TI1 and TI2
A quadrature encoder can be connected directly to the MCU without external interface logic.
However, comparators are normally be used to convert the encoder's differential outputs to
digital signals. This greatly increases noise immunity. The third encoder output which
indicate the mechanical zero position, may be connected to an external interrupt input and
trigger a counter reset.
The Figure 241
and direction control. It also shows how input jitter is compensated where both edges are
selected. This might occur if the sensor is positioned near to one of the switching points. For
this example we assume that the configuration is the following:
• CC1S='01' (TIMx_CCMR1 register, TI1FP1 mapped on TI1).
•
CC2S='01' (TIMx_CCMR2 register, TI1FP2 mapped on TI2).
• CC1P='0' and CC1NP='0' (TIMx_CCER register, TI1FP1 non-inverted, TI1FP1=TI1).
•
CC2P='0' and CC2NP='0' (TIMx_CCER register, TI1FP2 non-inverted, TI1FP2= TI2).
• SMS='011' (TIMx_SMCR register, both inputs are active on both rising and falling
edges).
•
CEN='1' (TIMx_CR1 register, Counter enabled).

Table 147. Counting direction versus encoder signals

Level on
opposite
signal (TI1FP1
for TI2,
TI2FP2 for
TI1)
High
Low
High
Low
High
Low
gives an example of counter operation, showing count signal generation

Figure 241. Example of counter operation in encoder interface mode.

DocID024597 Rev 3
Advanced-control timers (TIM1/TIM8)
TI1FP1 signal
Rising Falling
Down Up
Up Down
No Count No Count
No Count No Count
Down Up
Up Down
TI2FP2 signal
Rising Falling
No Count No Count
No Count No Count
Up Down
Down Up
Up Down
Down Up
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