7540 datasheet(219/366 Pages) RENESAS

219 / 366 page

2-143

REJ09B0018-0200Z

Rev.2.00

Jun 21, 2004

7540 Group

APPLICATION

2.9 Reset

Fig. 2.9.10 Example of mode transition

(1) Example of control procedure

Outline: The on-chip oscillator is used, and the intermittent operation for the low-power dissipation

can be realized.

Specifications: A mode is selected from the following modes 1 to 4 according to the usage condition.

The return from mode 1 is executed by the timer A interrupt request which occurs

every 0.5 s.

Mode 1: Wait mode by the on-chip oscillator oscillation

Operation clock source: On-chip oscillator

CPU stop, ceramic oscillation stop, on-chip oscillator oscillation

Mode 2: Middle-speed mode by the on-chip oscillator oscillation

Operation clock source: On-chip oscillator

CPU operation, ceramic oscillation stop, on-chip oscillator oscillation

Mode 3: Middle-speed mode by the ceramic oscillation

Operation clock source: Ceramic oscillation

CPU operation, ceramic oscillation, on-chip oscillator oscillation

Mode 4: Double-speed mode by the ceramic oscillation

Operation clock source: Ceramic oscillation

CPU operation, ceramic oscillation, on-chip oscillator oscillation

Figure 2.9.10 shows an example of mode transition and Figure 2.9.11 shows an example of control

procedure.

Time

Mode 1

Mode 2

Mode 1

Mode 2

Mode 1

Mode 2

Mode 3

Mode 1

Mode 2

CPU operation is started

by interrupt of timer

underflow

Ceramic oscillation start

Middle-speed mode (1/8)

Mode 4

Ceramic oscillation

Double-speed mode (1/1)

Wait mode by

on-chip oscillation

• CPU stop

• TImer operating

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