4501 datasheet(141/212 Pages) RENESAS

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2.3 Timers

2-24

Rev.2.01

Feb 07, 2005

4501 Group

APPLICATION

REJ09B0192-0201

2.3.3 Timer application examples

(1)

Timer operation: measurement of constant period

The constant period by the setting timer count value can be measured.

Outline: The constant period by the timer 1 underflow signal can be measured.

Specifications: Timer 1 and prescaler divides the system clock frequency f(XIN) = 4.0 MHz, and the

timer 1 interrupt request occurs every 3 ms.

Figure 2.3.3 shows the setting example of the constant period measurement.

(2)

CNTR output operation: piezoelectric buzzer output

Outline: Square wave output from timer 1 can be used for piezoelectric buzzer output.

Specifications: 4 kHz square wave is output from the CNTR pin at system clock frequency f(XIN)

= 4.0 MHz. Also, timer 1 interrupt occurs simultaneously.

Figure 2.3.1 shows the peripheral circuit example, and Figure 2.3.4 shows the setting example of

CNTR output.

Fig. 2.3.1 Peripheral circuit example

(3)

CNTR input operation: event count

Outline: Count operation can be performed by using the signal (falling waveform) input from CNTR

pin as the event.

Specifications: The low-frequency pulse from external as the timer 2 count source is input to CNTR

pin, and the timer 2 interrupt request occurs every 100 counts.

Figure 2.3.5 shows the setting example of CNTR input.

4501

CNTR

125

µs125 µs

Set dividing ratio for timer 1 underflow cycle to 125

µs.

In order to reduce the current dissipation, output is high-impedance state during buzzer output stop.

4501 Datasheet(PDF) 141 Page - Renesas Technology Corp