NEC switch - Manual (Page 172)

CHAPTER 11 INTERRUPT FUNCTIONS
User’s Manual U12978EJ3V0UD
172
Figure 11-8. Flowchart of Non-Maskable Interrupt Request Acknowledgment
Start
WDTM4 = 1
(watchdog timer mode
is selected)
Interval timer
No
WDT
overflows
No
Yes
Reset processing
No
Yes
Yes
Interrupt request is generated
Interrupt servicing is started
WDTM3 = 0
(non-maskable interrupt
is selected)
WDTM: Watchdog timer mode register
WDT: Watchdog timer
Figure 11-9. Timing of Non-Maskable Interrupt Request Acknowledgment
Instruction Instruction
Save PSW and PC, and
jump to interrupt servicing
Interrupt servicing program CPU processing
TMIF4
Figure 11-10. Acknowledging Non-Maskable Interrupt Request
Second interrupt servicing
First interrupt servicing
NMI request
(second)
NMI request
(first)
Main routine