NEC UPD789426 Series User Manual page 276

8-bit single-chip microcontrollers
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Figure 14-9. Flow from Generation of Non-Maskable Interrupt Request to Acknowledgment
Figure 14-10. Timing of Non-Maskable Interrupt Request Acknowledgment
CPU processing
Instruction
WDTIF
Figure 14-11. Non-Maskable Interrupt Request Acknowledgment
Main routine
NMI request
(first)
CHAPTER 14 INTERRUPT FUNCTIONS
Start
WDTM4 = 1
(watchdog timer mode
is selected)
Yes
WDT
overflows
Yes
WDTM3 = 0
(non-maskable interrupt
is selected)
Yes
Interrupt request is generated
Interrupt servicing starts
WDTM: Watchdog timer mode register
WDT:
Watchdog timer
Instruction
NMI request
(second)
User's Manual U15075EJ2V1UD
No
Interval timer
No
No
Reset processing
Saving PSW and PC, and
jump to interrupt servicing
First interrupt servicing
Second interrupt servicing
Interrupt servicing program
277

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