R8CSLASH2G datasheet(225/344 Pages) RENESAS

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R8C/2G Group

17. Timers

Rev.1.00

Apr 04, 2008

Page 205 of 318

REJ09B0387-0100

17.4.1

Input Capture Mode

In input capture mode, the edge of the TRFI pin input signal or fC32 is used as a trigger to latch the timer value

and the width or the period of external signal is measured. The TRFI input is equipped with a digital filter, and

this prevents errors caused by noise or the like from occurring. Table 17.14 shows the Input Capture Mode

Specifications. Figure 17.52 shows an Operating Example in Input Capture Mode.

Table 17.14

Input Capture Mode Specifications

Item

Specification

Count sources

f1, f8, f32

Count operations

• Increment

• Transfer the value in the TRF register to the TRFM0 register at the valid

edge of the measured pulse.

Count period

1/fk × 65536 fk: Frequency of count source

Count start condition

The TSTART bit in the TRFCR0 register is set to 1 (count starts).

Count stop condition

The TSTART bit in the TRFCR0 register is set to 0 (count stops).

Interrupt request

generation timing

• The valid edge of TRFI input or fC32 [capture interrupt]

• When timer RF overflows [timer RF interrupt]

TRFI pin function

Measured pulse input

TRFO00 to TRFO02,

TRFO11 to TRFO12 pin

functions

Programmable I/O port

Counter value reset timing In the following cases, the value in the TRF register is set to 0000h.

• When the TSTART bit in the TRFCR0 register is set to 0 (count stops).

Read from timer

• The count value can be read out by reading the TRF register.

• The count value at the measured pulse valid edge input can be read out by

reading the TRFM0 register.

Write to timer

Write to the TRF and TRFM0 registers is disabled.

Select functions

• TRFI or fC32 polarity selected

Selects the valid edge of the measured pulse.

(Bits TRFC03 to TRFC04 in the TRFCR0 register.)

• Digital filter function

The TRFI input is sampled, and when the sampled input level matches as

three times, the level is determined.

Selects the sampling clock of the digital filter.

(Bits TIPF0 to TIPF1 in the TRFCR1 register.)

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