NEC PD78212 User Manual page 339

µ PD78214 Sub-Series
(c) 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 after the NMI request occurs)
(d) If two new NMI requests occur during execution of an NMI service program (when the NMIS bit is not
manipulated by the current NMI service program)
Cautions 1. A macro service request is accepted and processed even when a nonmaskable interrupt service program is running. To disable
macro service processing during execution of the nonmaskable interrupt service program, cause the nonmaskable interrupt
service program to manipulate the mask register so that no macro service will not occur.
2. If the IE bit of the PSW is set to 1, for example, by executing the EI instruction in the nonmaskable interrupt service program,
maskable interrupt requests assigned high priority are made acceptable. If a maskable interrupt with high priority occurs during
execution of the nonmaskable interrupt service program, a service program for the maskable interrupt runs. If the IE and ISP
bits of the PSW are set to 1, interrupt requests with low priority will also occur, thus causing the interrupt service program to
run. An RETI instruction will be used to return from the maskable interrupt service program. The RETI instruction resets the
NMIS bit to 0, thus enabling nonmaskable interrupt requests even when multiple-interrupt handling should not be performed
for nonmaskable interrupts during execution of the nonmaskable interrupt service program to which a return was just made.
To inhibit multiple-interrupt handling for nonmaskable interrupt requests, do not enable interrupts during execution of the
nonmaskable interrupt service program.
310
Main routine
NMI
request
NMIS←0
NMI request
Main routine
N
MI
request
NMI request
N
MI
request
Pending NMI request is
accepted when NMIS = 0.
(NMIS = 1)
Pending,
because NMIS = 1
(NMIS = 1)
Pending, because NMIS = 1
Pending, because NMIS = 1
Although NMI request is issued
more than once, it is accepted
only once.