ST72344S2 datasheet(98/247 Pages) STMICROELECTRONICS

98 / 247 page

On-chip peripherals

ST72344xx, ST2345xx

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Doc ID 12321 Rev 6

Input capture

In this section, the index, i, may be 1 or 2 because there are 2 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.

ICiR register is a read-only register. The active transition is software-programmable through

the IEDGi bit of Control Registers (CRi). The 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]) (see Table 50: Clock control bits).

●

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

pin must be configured as floating input).

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

ICAP1pin must be configured as floating input).

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 48).

●

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 (i.e. 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 ICiLR register.

Note:

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

be 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 2 input capture functions can be used together even if the timer also uses the 2 output

compare functions.

In One-pulse Mode and PWM mode only the input capture 2 can be used.

The alternate inputs (ICAP1 & 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 pins is configured as an input and the second one as an

output, an interrupt can be generated provided that the user toggles the output pin and that

Table 45.

ICiR register

MS Byte

LS Byte

ICiR

ICiHR

ICiLR

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