ST72361AR4-Auto datasheet(128/279 Pages) STMICROELECTRONICS

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8-bit timer (TIM8)

ST72361xx-Auto

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Doc ID 12468 Rev 3

13.3.2

Input capture

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

the 8-bit timer.

The two 8-bit input capture registers (IC1R and IC2R) are used to latch the value of the free

running counter after a transition is detected on the ICAPi pin (see Figure 63).

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 (see Table 55).

Procedure

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

●

Select the timer clock (CC[1:0]) (see Table 55).

●

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

pin must be configured as floating input or input with pull-up without interrupt if this

configuration is available).

And 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 ICAP1

pin must be configured as floating input or input with pull-up without interrupt if this

configuration is available).

When an input capture occurs:

●

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 64).

●

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

the CC register. Otherwise, the interrupt remains pending until both conditions become

true.

Clearing the Input Capture interrupt request (that is, clearing the ICFi bit) is done in two

steps:

Reading the SR register while the ICFi bit is set.

An access (read or write) to the ICiR register.

Note:

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.

Once the ICIE bit is set both input capture features may trigger interrupt requests. If only

one is needed in the application, the interrupt routine software needs to discard the

unwanted capture interrupt. This can be done by checking the ICF1 and ICF2 flags and

resetting them both.

In One pulse Mode and PWM mode only 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 activates the input capture function.

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