UPD17P136ACT datasheet(146/292 Pages) NEC

146 / 292 page

CHAPTER 13 PERIPHERAL HARDWARE

127

(3) Program example of watchdog timer

Program Example

Notes 1.

Interrupt processing by BTM cannot be performed in the method to reset counter before BTM overflows.

Although the method of resetting the watchdog timer by using the BTM interrupt processing is easier

to program than the other two methods, its program hang-up detection rate is lower than that of the

other two.

Start

Initialize

Main Processing

ORG

INITJOB:

INITFLG

SET1

SET2

SET1

CLR1

MAIN:

CALL

END

JOB1:

CLR1 IPBTM

SET1 BTMRES

SET IPBTM

RET

JOB2:

CLR2 IPBTM

SET1 WDTRES

SET IPBTM

RET

SET1 WDTRES

INTBTMJOB:

SET1 WDTRES

RETI

Reset BTM before its

count value reaches

to 128Note 1.

Reset watchdog timer

before its count value

reaches to 184.

Reset watchdog timer by

using interrupt processing

of BTMNote 2.

; BTM interrupt enable

INITJOB

INTBTMJOB

NOT BTMISEL, BTMRES, NOT BTMCK1, BTMCK0

BTMRES

WDTRES, WDTEN; Watchdog timer start

IPBTM

IRQBTM

JOB1

JOB2

UPD17P136ACT Datasheet(PDF) 146 Page - NEC

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