SH7721 datasheet(531/1524 Pages) RENESAS

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Section 12 Watchdog Timer (WDT)

WDTS300B_000020030200

Rev. 3.00 Jan. 18, 2008 Page 469 of 1458

REJ09B0033-0300

Section 12 Watchdog Timer (WDT)

This LSI includes the watchdog timer (WDT).

This LSI can be reset by the overflow of the counter when the value of the counter has not been

updated because of a system runaway.

The WDT is a single-channel timer that uses a peripheral clock as an input and counts the clock

settling time when clearing software standby mode and temporary standbys, such as frequency

changes. It can also be used as an interval timer.

12.1

Features

The WDT has the following features:

• Can be used to ensure the clock settling time: Use the WDT to cancel software standby mode

and the temporary standbys which occur when the clock frequency is changed.

• Can switch between watchdog timer mode and interval timer mode.

• Generates internal resets in watchdog timer mode: Internal resets occur after counter overflow.

• An interrupt is generated in interval timer mode

An interval timer interrupt is generated when the counter overflows.

• Choice of eight counter input clocks

Eight clocks (

×1 to ×1/4096) that are obtained by dividing the peripheral clock can be chosen.

• Choice of two resets

Power-on reset and manual reset are available.

SH7721 Datasheet(PDF) 531 Page - Renesas Technology Corp