NEC PD78214 - Manual (Page 412)

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Chapter 14 Standby Function
14
Fig. 14-4 Releasing STOP Mode with an NMI Signal
Caution If another effective edge of the NMI signal is detected during the oscillation settling time, the oscillation settling time counter is
cleared and restarts counting, resulting in a longer wait time than usual. The extra wait time is the total of the time from the end
of the first active level to detection of the next effective edge and the width of the second active level, starting from its effective
edge. Fix the NMI signal at the inactive level during the oscillation settling time, to ensure the release of STOP mode.
Fig. 14-5 Example of Longer Oscillation Settling Time
(2) Releasing STOP mode by RESET input
The oscillator restarts when the RESET signal is changed from high to low to set the system to the reset state.
Keep the RESET signal active until the oscillation settling time has elapsed. When the RESET signal goes high,
normal operation starts.
Unlike ordinary reset, the contents of data memory will be the same as those existing immediately before the
system enters STOP mode.
★
NMI
(effective at falling edge)
2 16 /f CLK
STOP mode Wait for oscillation to settle Normal operation
Oscillation settling time
is extended by this period.
CPU operation
Count value of
oscillation settling
time counter
Cleared by
effective edge
STOP
Oscillator
f
CLK
STP flip-flop 1
STP flip-flop 2
NMI input
(effective at rising edge)
Oscillator stops Count time for
oscillation settling time counter