7733 datasheet(883/940 Pages) RENESAS

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17–3

APPLICATIONS

7736 Group User’s Manual

17.4 Power saving

Power saving examples (in other words, examples to save power consumption) with the stop or wait mode

used in external bus mode A are described below. The following examples differ from examples in external

bus mode B only in external bus pins allocated to ports P0 to P3. Therefore, for power saving in external

bus mode B, refer to this section.

17.4.1 Power saving example with stop mode used

In this example, power saving is realized by using the stop mode. The stop mode is terminated by using

the key input interrupt function.

(1) Specifications

The microcomputer operates in the single-chip mode.

Pins P100 to P103 are used as output pins for the key matrix scanning.

Input pins (KI0 to KI3) for the key input interrupt function are used as key input pins.

Pins KI0 to KI3 are pulled high by using the pull-up function.

The initial output levels of pins P100 to P103 are “L.”

When a key input interrupt request occurs owing to a key push, the key data is read-in. (This

reading is surely performed independent of power saving.)

In the stop mode, interrupts other than a key input interrupt are disabled.

An external clock is used as the main clock.

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