H8SSLASH2240 datasheet(429/818 Pages) RENESAS

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Section 11 Watchdog Timer

Rev.3.00 Mar. 26, 2007 Page 387 of 772

REJ09B0355-0300

Section 11 Watchdog Timer

11.1

Overview

The H8S/2245 Group has a single-channel on-chip watchdog timer (WDT) for monitoring system

operation. The WDT outputs an overflow signal (

WDTOVF) if a system crash prevents the CPU

from writing to the timer counter, allowing it to overflow. At the same time, the WDT can also

generate an internal reset signal for the H8S/2245 Group.

When this watchdog function is not needed, the WDT can be used as an interval timer. In interval

timer operation, an interval timer interrupt is generated each time the counter overflows.

11.1.1

Features

WDT features are listed below.

• Switchable between watchdog timer mode and interval timer mode

• WDTOVF output when in watchdog timer mode

If the counter overflows, the WDT outputs

WDTOVF. It is possible to select whether or not

the entire H8S/2245 Group is reset at the same time. This internal reset can be a power-on reset

or a manual reset.

• Interrupt generation when in interval timer mode

If the counter overflows, the WDT generates an interval timer interrupt.

• Choice of eight counter clock sources.

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