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