NEC UPD703116 User Manual page 162

Figure 7-2. Acknowledging Non-Maskable Interrupt Request
(a) If a new NMI request is generated while an NMI service program is being executed
NMI request
(b) If a new NMI request is generated twice while an NMI service program is being executed
Main routine
NMI request
162
CHAPTER 7 INTERRUPT/EXCEPTION PROCESSING FUNCTION
Main routine
NMI request
NMI request Held pending because NMI service program is being processed
NMI request
Held pending because NMI service program is being processed
Only one NMI request is acknowledged even though
two NMI requests are generated
User's Manual U14492EJ5V0UD
(PSW.NP = 1)
NMI request held pending regardless
of the value of the NP bit of the PSW
Pending NMI request processed