7643 datasheet(140/424 Pages) RENESAS

140 / 424 page

Rev.2.00

Aug 28, 2006

page 19 of 202

7643 Group

REJ09B0133-0200

APPLICATION

2.2 Timer

(3) Timer application example 2: Piezoelectric buzzer output

Outline: The rectangular waveform output function of the timer is applied for a piezoelectric buzzer

output.

Specifications: •The rectangular waveform, dividing the clock f(XIN) = 4.19 MHz (222 Hz) into about

2 kHz (2048 Hz), is output from the P51/TOUT/XCOUT pin.

•The level of the P51/TOUT/XCOUT pin is fixed to “H” while a piezoelectric buzzer

output stops.

Figure 2.2.11 shows a peripheral circuit example, and Figure 2.2.12 shows the timers connection

and setting of division ratios. Figure 2.2.13 shows the related registers setting, and Figure 2.2.14

shows the control procedure.

Fig. 2.2.11 Peripheral circuit example

Fig. 2.2.12 Timers connection and setting of division ratios

f(XIN)

4.19 MHz

1/2

1/8

1/64

Count source

selection

φ / 8

Timer 1

1/2

Fixed

P51/TOUT/XCOUT

7643 Group

P51/TOUT/XCOUT

PiPiPi.....

244

µs

TOUT output

The “H” level is output while a piezoelectric buzzer output stops.

244

µs

Set a division ratio so that the underflow

output period of the timer 1 can be 244

µs.

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