NEC PD78214 - Manual (Page 338)

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Chapter 12 Interrupt Functions
12
Resetting the NMIS bit to 0 during execution of a nonmaskable interrupt service program enables multiple-
interrupt handling for nonmaskable interrupt requests. If the NMIS bit is 0, a new nonmaskable interrupt request
is accepted even when a nonmaskable interrupt service program is running.
Fig. 12-9 Accepting an NMI Interrupt Request
(a) If a new NMI request occurs during execution of an NMI service program (when the IST register is not
manipulated)
Main routine
(NMIS = 1)
NMI request pending because NMIS = 1
Processing pending NMI request
NMI request
NMI request
(b) If a new NMI request occurs during execution of an NMI service program (when the NMIS bit is reset to 0 by
the current NMI service program)
Main routine
(NMIS = 1)
NMI request NMI request
NMIS ←0