
CHAPTER 24 STANDBY FUNCTION
Preliminary User’s Manual U16541EJ1V0UM
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24.3 IDLE1 Mode
24.3.1 Setting and operation status
The IDLE1 mode is set by clearing the PSM1 and PSM0 bits of the PSMR register to 00 and setting the STP bit of
the PSC register to 1 in the normal operation mode.
In the IDLE1 mode, the clock oscillator, PLL operation, and flash memory continue operating but clock supply to
the CPU and other on-chip peripheral functions stops.
As a result, program execution stops and the contents of the internal RAM before the IDLE1 mode was set are
retained. The CPU and other on-chip peripheral functions stop operating. However, the on-chip peripheral functions
that can operate with the subclock or an external clock continue operating.
Table 24-5 shows the operation status in the IDLE1 mode.
The IDLE1 mode can reduce the current consumption more than the HALT mode because it stops the operation of
the on-chip peripheral functions. The main clock oscillator does not stop, so the normal operation mode can be
restored without waiting for the oscillation stabilization time after the IDLE1 mode has been released, in the same
manner as when the HALT mode is released.
Caution
Insert five or more NOP instructions after the instruction that stores data in the PSC register to
set the IDLE1 mode.
24.3.2 Releasing IDLE1 mode
The IDLE1 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 a peripheral function operable in the IDLE1 mode, or reset signal (reset by RESET pin input, WDT2RES signal,
low-voltage detector (LVI), or clock monitor (CLM)).
After the IDLE1 mode has been released, the normal operation mode is restored.
(1) Releasing IDLE1 mode by non-maskable interrupt request signal or unmasked maskable interrupt
request signal
The IDLE1 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 IDLE1 mode is set in an interrupt
servicing routine, however, an interrupt request signal that is issued later is processed as follows.
Caution
An interrupt request signal that is disabled by setting the NMI1M, NMI0M, and INTM bits of
the PSC register to 1 becomes invalid and IDLE1 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 IDLE1 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 IDLE1 mode is released and
that interrupt request signal is acknowledged.