CHAPTER 8 CLOCK GENERATION FUNCTION
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User’s Manual U15195EJ5V0UD
(2) Release of software STOP mode
Software STOP mode is released by a non-maskable interrupt request, an unmasked maskable interrupt
request (INTPn)
Note
, or RESET pin input. Also, to release software STOP mode when PLL mode (CKSEL pin
= low level) and resonator connection mode (CESEL bit of CKC register = 0) are used, the oscillator’s
oscillation stabilization time must be secured (n = 0 to 4, 20 to 25)
Moreover, the oscillation stabilization time must be secured even when an external clock is connected
(CESEL bit = 1). See
8.4 PLL Lockup
for details.
Note
When a digital filter using clock sampling is selected as the noise eliminator for INTP20 to INTP25,
software STOP mode cannot be released.
(a) Release by a non-maskable interrupt request or an unmasked maskable interrupt request
Software STOP mode is released by an interrupt request only when transition to software STOP mode is
performed with the INTM and NMIM bits of the PSC register set to 0.
Software STOP mode is released by a non-maskable interrupt request or by an unmasked maskable
interrupt request (INTPn) regardless of the priority (n = 0 to 4, 20 to 25). The operation after release is as
follows.
Caution When the NMIM and INTM bits of the PSC register = 1, the software STOP mode cannot
be released by the non-maskable interrupt request signal and unmasked maskable
interrupt request signal.
Table 8-7. Operation After Software STOP Mode Is Released by Interrupt Request
Cancellation Source
Enable Interrupt (EI) Status
Disable Interrupt (DI) Status
Non-maskable interrupt request
Branch to handler address
Maskable interrupt request
Branch to handler address or
execute next instruction
Execute next instruction
If the system is set to software STOP mode during an interrupt servicing routine, operation will differ as
follows.
(i) If an interrupt request is generated with a lower priority than that of the interrupt request that is
currently being servicing, software STOP mode is released, but the newly generated interrupt
request is not acknowledged. The new interrupt request is held pending.
(ii) If an interrupt request (including non-maskable interrupt requests) is generated with a higher priority
than that of the interrupt request that is currently being serviced, software STOP mode is released
and the newly generated interrupt request is acknowledged.
If the system is set to software STOP mode during an NMI servicing routine, software STOP mode is
released, but the interrupt is not acknowledged (interrupt is held pending).
Interrupt servicing that is started when software STOP mode is released by NMI pin input is handled in
the same way as normal NMI interrupt servicing that occurs during an emergency (because the NMI
interrupt handler address is unique). Therefore, when a program must be able to distinguish between
these two situations, a software status must be prepared in advance and that status must be set before
setting the PSMR register using a store instruction or a bit manipulation instruction.
By checking for this status during NMI interrupt servicing, an ordinary NMI can be distinguished from the
servicing that is started when software STOP mode is released by NMI pin input.
(b) Release by RESET pin input
This is the same as a normal reset operation.