ST72561J4-Auto datasheet(109/324 Pages) STMICROELECTRONICS

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ST72561-Auto

16-bit timer

Doc ID 12370 Rev 8

109/324

The active transition is software programmable through the IEDGi bit in the control register

(CRi).

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

12.3.4

Procedure

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

●

Select the timer clock (CC[1:0]) (see Table 50).

●

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

ICAP1pin 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 53).

●

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:

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 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 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.

Moreover if one of the ICAPi pins is configured as an input and the second one as an output,

an interrupt can be generated if the user toggles the output pin and if the ICIE bit is set.

This can be avoided if the input capture function i is disabled by reading the ICiHR

(see note 1).

The TOF bit can be used with interrupt generation in order to measure events that go

beyond the timer range (FFFFh).

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