R8CSLASH20 datasheet(149/501 Pages) RENESAS

149 / 501 page

R8C/20 Group, R8C/21 Group

14. Timers

Rev.2.00 Aug 27, 2008

Page 133 of 458

REJ09B0250-0200

14.1.5

Pulse Period Measurement Mode

Pulse period measurement mode is mode to measure the pulse period of an external signal which inputs from

the INT1/TRAIO pin (see Table 14.6 Pulse Period Measurement Mode Specifications).

Figure 14.11 shows the TRAIOC Register in Pulse Period Measurement Mode and Figure 14.12 shows the

Operating Example of Pulse Period Measurement Mode.

NOTE:

1. Input the pulse whose period is longer than twice of the timer RA prescaler period. Input the longer

pulse for “H” width and “L” width than the timer RA prescaler period. If the shorter pulse than the

period is input to the TRAIO pin, the input may be disabled.

Table 14.6

Pulse Period Measurement Mode Specifications

Item

Specification

Count Sources

f1, f2, f8, fOCO

Count Operations

• Decrement

• After an active edge of measurement pulse is input, contents for the read-out

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

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

prescaler and continues counting.

Count Start Condition

Write 1 (count start) to the TSTART bit in the TRACR register

Count Stop Conditions

• Write 0 (count stop) to TSTART bit in the TRACR register

• Write 1 (count forcibly stops) 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

Measurement pulse input(1) (INT1 interrupt input)

TRAO Pin Function

Programmable I/O port

Read from Timer

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

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 14.1.1.1 Timer Write

Control during Count Operation).

Select Functions

• Measurement level select

The TEDGSEL bit in the TRAIOC register can select the measurement

period of input pulse.

• Measurement 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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