
3850 Group (Spec. H) User’s Manual
APPLICATION
2-99
2.10 Standby function
Fig. 2.10.3 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 for approximately 8,000 cycles of the XIN input is reserved at restoration from the stop mode.
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: f(XIN)/16 or f(XCIN)/16 is input as the prescaler 12 count source.
qWhen restoring microcomputer from stop mode by INT0 interrupt (rising edge selected)