R29 datasheet(210/473 Pages) RENESAS

210 / 473 page

R8C/28 Group, R8C/29 Group

14. Timers

Rev.2.10

Sep 26, 2008

Page 191 of 441

REJ09B0279-0210

14.3.4

Timer Mode (Input Capture Function)

This function measures the width or period of an external signal. An external signal input to the TRCIOj (j = A,

B, C, or D) pin acts as a trigger for transferring the contents of the TRC register (counter) to the TRCGRj

individual pin.

The TRCGRA register can also select fOCO128 signal as input-capture trigger input.

Table 14.16 lists the Specifications of Input Capture Function, Figure 14.42 shows a Block Diagram of Input

Capture Function, Figures 14.43 and 14.44 show the registers associated with the input capture function, Table

14.17 lists the Functions of TRCGRj Register when Using Input Capture Function, and Figure 14.45 shows an

Operating Example of Input Capture Function.

j = A, B, C, or D

Table 14.16

Specifications of Input Capture Function

Item

Specification

Count source

f1, f2, f4, f8, f32, fOCO40M, or external signal (rising edge) input to

TRCCLK pin

Count operation

Increment

Count period

1/fk × 65,536 fk: Count source frequency

Count start condition

1 (count starts) is written to the TSTART bit in the TRCMR register.

Count stop condition

0 (count stops) is written to the TSTART bit in the TRCMR register.

The TRC register retains a value before count stops.

Interrupt request generation

timing

• Input capture (valid edge of TRCIOj input or fOCO128 signal edge)

• The TRC register overflows.

TRCIOA, TRCIOB, TRCIOC,

and TRCIOD pin functions

Programmable I/O port or input capture input (selectable individually by

pin)

INT0 pin function

Programmable I/O port or INT0 interrupt input

Read from timer

The count value can be read by reading TRC register.

Write to timer

The TRC register can be written to.

Select functions

• Input capture input pin select

One or more of pins TRCIOA, TRCIOB, TRCIOC, and TRCIOD

• Input capture input valid edge selected

Rising edge, falling edge, or both rising and falling edges

• Buffer operation (Refer to 14.3.3.2 Buffer Operation.)

• Digital filter (Refer to 14.3.3.3 Digital Filter.)

• Input-capture trigger selected

fOCO128 can be selected for input-capture trigger input of the

TRCGRA register.

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