STM32W108CB datasheet(179/278 Pages) STMICROELECTRONICS

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STM32W108HB STM32W108CC STM32W108CB STM32W108CZ

General-purpose timers

Doc ID 16252 Rev 14

179/278

Counting on

TI1 only

Counting on

TI2 only

Counting on

TI1 and TI2

An external incremental encoder can be connected directly to the MCU without external

interface logic. However, comparators are normally used to convert an encoder's differential

outputs to digital signals, and this greatly increases noise immunity. If a third encoder output

indicates the mechanical zero (or index) position, it may be connected to an external

interrupt input and can trigger a counter reset.

Figure 39 gives an example of counter operation, showing count signal generation and

direction control. It also shows how input jitter is compensated for when both inputs are used

for counting. This might occur if the sensor is positioned near one of the switching points.

This example assumes the following configuration:

●

CC1S = 01 (TIMx_CCMR1 register, IC1FP1 mapped on TI1).

●

CC2S = 01 (TIMx_CCMR2 register, IC2FP2 mapped on TI2).

●

CC1P = 0 (TIMx_CCER register, IC1FP1 non-inverted, IC1FP1 = TI1).

●

CC2P = 0 (TIMx_CCER register, IC2FP2 non-inverted, IC2FP2 = TI2).

●

SMS = 011 (TIMx_SMCR register, both inputs are active on both rising and falling

edges).

●

CEN = 1 (TIMx_CR1 register, counter is enabled).

Figure 39.

Example of counter operation in encoder interface mode

Table 34.

Counting direction versus encoder signals

Active

edges

Level on opposite

signal (TI1FP1 for

TI2, TI2FP2 for

TI1)

TI1FP1 signal

TI2FP2 signal

Rising

Falling

Rising

Falling

High

Down

No Count

Low

Down

No Count

High

No Count

Down

Low

No Count

Down

High

Down

Low

Down

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