IBM uPD78082 - Manual (Page 206)

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CHAPTER 12 INTERRUPT FUNCTION
Figure 12-10. Non-Maskable Interrupt Request Acknowledge Operation
(a) If a new non-maskable interrupt request is generated during
non-maskable interrupt servicing program execution
(b) If two non-maskable interrupt requests are generated during
non-maskable interrupt servicing program execution
Main Routine
NMI Request ➀
1 Instruction
Execution
NMI Request ➁
NMI Request ➀ Execute
NMI Request ➁ Reserve
Reserved NMI Request Processing
Main Routine
NMI Request ➀
1 Instruction
Execution
NMI
Request ➁
NMI Request ➀ Execute
NMI Request ➁ Reserve
NMI Request ➂ Reserve
Reserved NMI Request ➁
Processing
Cannot acknowledge NMI Request ➂
(Although multiple NMI requests may
be generated twice or more, they
can only be acknowledged once.)
NMI
Request ➂