Single-Chip Microcontrollers User's Manual

492

CHAPTER 21 INTERRUPT AND TEST FUNCTIONS

WDTM4=1

(with watchdog timer

mode selected)?

Overflow in WDT?

WDTM3=0

(with non-maskable

interrupt selected)?

Interrupt request generation

WDT interrupt servicing?

Interrupt control

Interrupt

service start

Interrupt request

held pending

Reset processing

Interval timer

Start

Yes

Figure 21-10. Flowchart from the Time a Non-maskable Interrupt Request Is Generated Until

It Is Received

WDTM : Watchdog timer mode register

WDT : Watchdog timer

Figure 21-11. Non-Maskable Interrupt Request Acknowledge Timing

TMIF4: Watchdog Timer Interrupt Request Flag

Instruction Instruction CPU Processing

TMIF4

PSW and PC Save, Jump

to Interrupt Servicing

Interrupt Servicing

Program

Interrupt requests generated during this time are received

at the timing indicated by ↑.