7540 datasheet(128/366 Pages) RENESAS

128 / 366 page

2-52

REJ09B0018-0200Z

Rev.2.00

Jun 21, 2004

APPLICATION

7540 Group

2.4 Timer X

(3) Application example of pulse output mode

Outline: The pulse output mode of timer X is used for a piezoelectric buzzer output.

Specifications: The rectangular waveform which is clock f(XIN) = 4 MHz divided up to 4 kHZ is

output from the P14/CNTR0 pin.

The level of the P14/CNTR0 pin is fixed to “H” while a piezoelectric buzzer output is

stopped.

Operation clock: f(XIN) = 4 MHz, double-speed mode

Figure 2.4.15 shows an example of a peripheral circuit, Figure 2.4.16 shows the connection of timer

and setting of the division ratio, and Figure 2.4.17 shows an example of control procedure.

Fig. 2.4.15 Example of peripheral circuit

7540 Group

P14/CNTR0

PiPiPi.....

125

µs 125 µs

Set division ratio so that the underflow

output period of timer X will become

125

µs.

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

CNTR0 output

f(XIN) = 4MHz

Prescaler X

Timer X

1/2

Timer X count

source selection

bit

1/2

1/125

1/2

Fixed

CNTR0 pin output

4 kHz

Fig. 2.4.16 Connection of timer and setting of division ratio

7540 Datasheet(PDF) 128 Page - Renesas Technology Corp

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