M38044FFHKP datasheet(276/387 Pages) RENESAS

276 / 387 page

2-152

APPLICATION

2.12 Standby function

Rev.1.00 Jan 14, 2005

REJ09B0212-0100Z

3804 Group (Spec.H)

Fig. 2.12.2 Execution sequence example at restoration by occurrence of INT0 interrupt request

(3)

Notes on using stop mode

sRegister setting

Since values of the prescaler 12 and Timer 1 are automatically reloaded when returning from the

stop mode, set them again, respectively. (When the oscillation stabilizing time set after STP

instruction released bit is “0”)

sClock restoration

After restoration from the stop mode to the normal mode by an interrupt request, the contents of

the CPU mode register previous to the STP instruction execution are retained. Accordingly, if both

main clock and sub clock were oscillating before execution of the STP instruction, the oscillation

of both clocks is resumed at restoration.

In the above case, when the main clock side is set as a system clock, the oscillation stabilizing

time until the timer 1 underflow is reserved at restoration from the stop mode.

When the oscillation stabilizing time set after STP instruction released bit is “0”, the time for 512

counts of the count source become the oscillation stabilizing time. When the oscillation stabilizing

time set after STP instruction released bit is “1”, an arbitrarily count value set to the prescaler 12

and the timer 1 become the oscillation stabilizing time.

At this time, note that the oscillation on the sub clock side may not be stabilized even after the

lapse of the oscillation stabilizing time of the main clock side.

Stop mode

XIN or XCIN

(System clock)

INT0 pin

Prescaler 12 counter

Timer 1 counter

INT0 interrupt request bit

Peripheral device

CPU

Operating

Stopped

Operating

512 counts

Oscillation stabilizing time

XIN; “H”

XCIN; in high-impedance state

“FF16”

“0116”

Execute STP

instruction

INT0 interrupt signal

input (INT0 interrupt

request occurs)

Oscillation start

Prescaler 12 count start

512 counts down by

prescaler 12

Start supplying internal

clock

φ to CPU

Accept INT0 interrupt

request

Note: The count source set at STP instruction execution is connected as the prescaler 12 count source.

qWhen restoring microcomputer from stop mode by INT0 interrupt

(oscillation stabilizing time set after STP instruction released bit = “0”, rising edge selected)

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