7480 datasheet(249/337 Pages) RENESAS

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7480 Group and 7481 Group User's Manual

2-34

APPLICATIONS

2.7 Power-Saving Function

2.7.1 Application Example of Stop Mode

Power-Saving in Key-Input Waiting State

POINT: When the CPU has no key input for the specified period in its key-input waiting state, the

CPU enters the stop mode and reduces power dissipation by halting itself and its peripherals.

Any key input, thereafter, generates a key-on wakeup interrupt request, and the CPU returns

to the normal mode by accepting the request.

SPECIFICATIONS:

Port pin P00 is used as a key-input pin.

When having no key input for the specified period, the CPU executes the STP

instruction to enter the stop mode.

Any key input generates a key-on wakeup interrupt request in the stop mode,

and the CPU returns to the normal mode by accepting the request.

Figure 2.7.1 shows a connection example.

Figure 2.7.2 shows an operation example in the key-input waiting state.

Figure 2.7.3 shows a control procedure example of power-saving in key-input waiting state.

2.7 Power-Saving Function

Figure 2.7.1 Connection Example

Figure 2.7.2 Operation Example in Key-Input Waiting State

P00

7480 Group

7481 Group

Key input

STP instruction

executed

Key-on wakeup interrupt

request generated

Oscillator start-up stabilizing time

2048 count of XIN pin input signal

Key-input waiting state

after the specified period

Stop mode state

Port P0

Internal clock

XIN

Key input

Key-on wakeup interrupt

service routine executed

XIN pin : High-impedance state

STP instruction

execution cycle

Undefined

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