R8CSLASH2G datasheet(177/344 Pages) RENESAS

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R8C/2G Group

17. Timers

Rev.1.00

Apr 04, 2008

Page 157 of 318

REJ09B0387-0100

17.1.5

Pulse Period Measurement Mode

In pulse period measurement mode, the pulse period of an external signal input to the INT1/TRAIO pin is

measured (refer to Table 17.6 Pulse Period Measurement Mode Specifications).

Figure 17.10 shows TRAIOC Register in Pulse Period Measurement Mode and Figure 17.11 shows an

Operating Example of Pulse Period Measurement Mode.

NOTE:

1. Input a pulse with a period longer than twice the timer RA prescaler period. Input a pulse with a

longer “H” and “L” width than the timer RA prescaler period. If a pulse with a shorter period is input to

the TRAIO pin, the input may be ignored.

Table 17.6

Pulse Period Measurement Mode Specifications

Item

Specification

Count sources

f1, f2, f8, fOCO, fC32

Count operations

• Decrement

• After the active edge of the measured pulse is input, the contents of the read-

out buffer are retained at the first underflow of timer RA prescaler. Then timer

RA reloads the contents in the reload register at the second underflow of

timer RA prescaler and continues counting.

Count start condition

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

Count stop conditions

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

• 1 (count forcibly stops) is written to the TSTOP bit in the TRACR register.

Interrupt request

generation timing

• When timer RA underflows or reloads [timer RA interrupt].

• Rising or falling of the TRAIO input (end of measurement period) [timer RA

interrupt]

INT1/TRAIO pin function Measured pulse input(1) (INT1 interrupt input)

TRAO pin function

Programmable I/O port

Read from timer

The count value can be read by reading registers TRA and TRAPRE.

Write to timer

• When registers TRAPRE and TRA are written while the count is stopped,

values are written to both the reload register and counter.

• When registers TRAPRE and TRA are written during the count, values are

written to the reload register and counter (refer to 17.1.1.1 Timer Write

Control during Count Operation

Select functions

• Measurement period select

The TEDGSEL bit in the TRAIOC register selects the measurement period of

the input pulse.

• Measured pulse input pin select function

P1_7 or P1_5 is selected by the TIOSEL bit in the TRAIOC register.

• Digital filter function

Bits TIPF0 and TIPF1 in the TRAIOC register enable or disable the digital

filter and select the sampling frequency.

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