
CHAPTER 24 STANDBY FUNCTION
Preliminary User’s Manual U16541EJ1V0UM
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24.8 Sub-IDLE Mode
24.8.1 Setting and operation status
The sub-IDLE mode is set by setting the PSM1 and PSM0 bits of the PSMR register to 10 and setting the STP bit
of the PSC register to 1 in the subclock operation mode.
In this mode, the clock oscillator continues operation but clock supply to the CPU, flash memory, and the other on-
chip peripheral functions is stopped.
As a result, program execution stops and the contents of the internal RAM before the sub-IDLE mode was set are
retained. The CPU and the other on-chip peripheral functions are stopped. However, the on-chip peripheral functions
that can operate with the subclock or an external clock continue operating.
Because the sub-IDLE mode stops operation of the CPU, flash memory, and other on-chip peripheral functions, it
can reduce the current consumption more than the subclock operation mode. If the sub-IDLE mode is set after the
main clock has been stopped, the current consumption can be reduced to a level as low as that in the software STOP
mode.
Table 24-12 shows the operation status in the sub-IDLE mode.
24.8.2 Releasing sub-IDLE mode
The sub-IDLE mode is released by a non-maskable interrupt request signal (NMI pin input, INTWDT2 signal),
unmasked external interrupt request signal (INTP0 to INTP7 pin input), unmasked internal interrupt request signal
from the peripheral functions operable in the sub-IDLE mode, or reset signal (reset by RESET pin input, WDT2RES
signal, low-voltage detector (LVI), or clock monitor (CLM)). The PLL returns to the operation status before the sub-
IDLE mode was set.
When the sub-IDLE mode is released by an interrupt request signal, the subclock operation mode is set. If it is
released by reset signal, the normal operation mode is restored.
(1) Releasing sub-IDLE mode by non-maskable interrupt request signal or unmasked maskable interrupt
request signal
The sub-IDLE 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 signal.
If the sub-IDLE mode is set in an interrupt servicing routine, however, an interrupt request signal that is issued
later is serviced as follows.
Caution
The interrupt request signal that is disabled by setting the NMI1M, NMI0M, and INTM bits of
the PSC register to 1 becomes invalid and sub-IDLE mode is not released.
(a) If an interrupt request signal with a priority lower than that of the interrupt request currently being serviced
is issued, only the sub-IDLE 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 sub-IDLE mode is released and that
interrupt request signal is acknowledged.