ST7LITE49K2 datasheet(120/245 Pages) STMICROELECTRONICS

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On-chip peripherals

ST7LITE49K2

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Input capture

In this section, the index, i, may be 1 or 2 because there are two input capture functions in

the 16-bit timer.

The two input capture 16-bit registers (IC1R and IC2R) are used to latch the value of the

free-running counter after a transition detected by the ICAPi pin (see below).

ICiR register is a read-only register.

The active transition is software programmable through the IEDGi bit of control registers

(CRi).

Timing resolution is one count of the free running counter: (fCPU/CC[1:0]).

Procedure

To use the input capture function, select the following in the CR2 register:

●

Select the timer clock (CC[1:0]).

●

Select the edge of the active transition on the ICAP2 pin with the IEDG2 bit (the ICAP2

pin must be configured as floating input).

Select the following in the CR1 register:

●

Set the ICIE bit to generate an interrupt after an input capture coming from either the

ICAP1 pin or the ICAP2 pin

●

Select the edge of the active transition on the ICAP1 pin with the IEDG1 bit (the

ICAP1pin must be configured as floating input).

When an input capture occurs:

●

The ICFi bit is set

●

The ICiR register contains the value of the free running counter on the active transition

on the ICAPi pin (see Figure 61).

●

A timer interrupt is generated if the ICIE bit is set and the I bit is cleared in the CC

Clearing the input capture interrupt request (that is, clearing the ICFi bit) is done in two

steps:

By reading the SR register while the ICFi bit is set.

By accessing (reading or writing) the ICiLR register.

Note:

After reading the ICiHR register, transfer of input capture data is inhibited and ICFi is never

set until the ICiLR register is also read.

The ICiR register contains the free running counter value which corresponds to the most

recent input capture.

The two input capture functions can be used together even if the timer also uses the two

output compare functions.

In One Pulse mode and PWM mode only the input capture 2 can be used.

The alternate inputs (ICAP1 and ICAP2) are always directly connected to the timer. So any

transitions on these pins activate the input capture function. Moreover if one of the ICAPi pin

is configured as an input and the second one as an output, an interrupt can be generated if

MSB

LSB

ICiR

ICiHR

ICiLR

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