µPD61P24

15

15. AC PIN (ALL CLEAR PIN)

Internal part of the CPU including the program counter can be reset by setting the AC pin to the low level.

Watchdog Timer Function

A power-on reset function and a CR watchdog timer function, that can be controlled by program, can be realized

by connecting a 0.1

µF capacitor across the AC pin and the VSS.

V DD

0.1 F

µ

0.1 F

µ

V

V DD

V thL

t

Charge mode

Charge start instruction

Execute HALT instruction

immediately before NOP.

(Charge for 0.4 ms or more)

Discharge mode

Charge-discharge

pattern

Discharge start instruction

Discharge starts after the NOP

instruction execution.

(Discharge time is about 5 ms from VDD to VthL)

The pattern must be

controlled by the program,

in such a manner that

the C charge level will not

go below VthL.

Caution When the watchdog timer function is not used, switch to charging mode by executing a NOP

instruction immediately before a HALT instruction at the beginning of the program. (Be sure to

connect the capacitor.)