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CHAPTER 20 STANDBY FUNCTION
User’s Manual U19780EJ2V0UD
547
Cautions 1. To use the peripheral hardware that stops operation in the STOP mode, and the peripheral
hardware for which the clock that stops oscillating in the STOP mode after the STOP mode is
released, restart the peripheral hardware.
2. Even if “internal low-speed oscillator can be stopped by software” is selected by the option
byte, the internal low-speed oscillation clock continues in the STOP mode in the status before
the STOP mode is set. To stop the internal low-speed oscillator’s oscillation in the STOP mode,
stop it by software and then execute the STOP instruction.
3. To shorten oscillation stabilization time after the STOP mode is released when the CPU operates
with the high-speed system clock (X1 oscillation), switch the CPU clock to the internal high-
speed oscillation clock before the execution of the STOP instruction using the following
procedure.
<1> Set RSTOP to 0 (starting oscillation of the internal high-speed oscillator)
→
<2> Set MCM0
to 0 (switching the CPU from X1 oscillation to internal high-speed oscillation)
→
<3> Check that
MCS is 0 (checking the CPU clock)
→
<4> Check that RSTS is 1 (checking internal high-speed
oscillation operation)
→
<5> Execute the STOP instruction
Before changing the CPU clock from the internal high-speed oscillation clock to the high-speed
system clock (X1 oscillation) after the STOP mode is released, check the oscillation stabilization
time with the oscillation stabilization time counter status register (OSTC).
4. If the STOP instruction is executed when AMPH = 1, supply of the CPU clock is stopped for 4.06
to 16.12
μ
s after the STOP mode is released when the internal high-speed oscillation clock is
selected as the CPU clock, or for the duration of 160 external clocks when the high-speed
system clock (external clock input) is selected as the CPU clock.
5. Execute the STOP instruction after having confirmed that the internal high-speed oscillator is
operating stably (RSTS = 1).