M38044F2HKP datasheet(274/387 Pages) RENESAS

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2-150

APPLICATION

2.12 Standby function

Rev.1.00 Jan 14, 2005

REJ09B0212-0100Z

3804 Group (Spec.H)

(2)

Release of stop mode

The stop mode is released by a reset input or by the occurrence of an interrupt request. Note the

differences in the restoration process according to reset input or interrupt request, as described

below.

sRestoration by reset input

The stop mode is released by holding the RESET pin to the “L” input level during the stop mode.

Oscillation is started when all ports are in the input state and the stop mode of the main clock (XIN-

XOUT) is released.

Oscillation is unstable when restarted. For this reason, time for stabilizing of oscillation (oscillation

stabilizing time) is required. The input of the RESET pin should be held at the “L” level until oscillation

stabilizes.

When the RESET pin is held at the “L” level for 16 cycles or more of XIN after the oscillation has

stabilized, the microcomputer will go to the reset state. After the input level of the RESET pin is

returned to “H”, the reset state is released in approximately 10.5 to 18.5 cycles of the XIN input.

Figure 2.12.1 shows the oscillation stabilizing time at restoration by reset input.

At release of the stop mode by reset input, the internal RAM retains its contents previous to the

reset. However, the previous contents of the CPU register and SFR are not retained.

For more details concerning reset, refer to “2.10 Reset”.

Fig. 2.12.1 Oscillation stabilizing time at restoration by reset input

Vcc

RESET

XIN

Stop mode

Oscillation

stabilizing time

16 cycles or

more of XIN

Operating mode

Time to hold internal reset state =

approximately 10.5 to 18.5 cycles of XIN input

Execute Stop instruction

(Note)

Note: Some cases may occur in which no waveform is input to XIN (in low-speed mode).

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