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CHAPTER 22 STANDBY FUNCTION
User’s Manual U16890EJ1V0UD
639
22.5 STOP Mode
22.5.1 Setting and operation status
The STOP mode is set when the PSMR.PSM bit is set to 1 and the PSC.STP bit is set to 1 in the normal operation
mode.
In the STOP mode, the subclock oscillator continues operating but the main clock oscillator stops. Clock supply to
the CPU and the on-chip peripheral functions is stopped.
As a result, program execution is stopped, and the contents of the internal RAM before the STOP mode was set
are retained. The on-chip peripheral functions that operate with the clock oscillated by the subclock oscillator or an
external clock continue operating.
Table 22-7 shows the operation status in the STOP mode.
Because the STOP stops operation of the main clock oscillator, it reduces the power consumption to a level lower
than the IDLE mode. If the subclock oscillator and external clock are not used, the power consumption can be
minimized with only leakage current flowing.
Caution Insert five or more NOP instructions after the instruction that stores data in the PSC register to
set the STOP mode.
22.5.2 Releasing STOP mode
The STOP mode is released by a non-maskable interrupt request signal (NMI pin input, INTWDT2 signal (when the
CPU is operating on the subclock)), unmasked external interrupt request signal (INTP0 to INTP6 pin input), unmasked
internal interrupt request signal from the peripheral functions operable in the STOP mode, or reset (RESET pin input,
WDTRES2 signal (when the CPU is operating on the subclock)).
After the STOP mode has been released, the normal operation mode is restored after the oscillation stabilization
time has been secured.
(1) Releasing STOP mode by non-maskable interrupt request signal or unmasked maskable interrupt
request signal
The STOP mode is released by a non-maskable interrupt request signal or an unmasked maskable interrupt
request signal, regardless of the priority of the interrupt request. If the software STOP mode is set in an
interrupt servicing routine, however, an interrupt request that is issued later is serviced as follows.
(a) If an interrupt request signal with a priority lower than that of the interrupt request currently being serviced
is issued, only the STOP mode is released, and that interrupt request signal is not acknowledged. The
interrupt request signal itself is retained.
(b) If an interrupt request signal with a priority higher than that of the interrupt request currently being
serviced is issued (including a non-maskable interrupt request signal), the STOP mode is released and
that interrupt request signal is acknowledged.
Table 22-6. Operation After Releasing STOP Mode by Interrupt Request Signal
Release Source
Interrupt Enabled (EI) Status
Interrupt Disabled (DI) Status
Non-maskable interrupt request signal
Execution branches to the handler address
Maskable interrupt request signal
Execution branches to the handler
address or the next instruction is executed
The next instruction is executed
(2) Releasing STOP mode by reset
The same operation as the normal reset operation is performed.