Electronics America 8-Bit Single-Chip Microcontrollers User's Manual

498

CHAPTER 21 INTERRUPT AND TEST FUNCTIONS

WDTM4=1

(with watchdog timer

mode selected)?

Overflow in WDT?

WDTM3=0

(with non-maskable

interrupt request

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 of Generation from Non-Maskable Interrupt Request to Acknowledgment

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 Instruction

TMIF4

PSW and PC Save, Jump

to Interrupt Servicing

Interrupt Sevicing

Program

The interrupt request generated during this period is acknowledged at the timing of ↑.