Datasheet

Section 13 Watchdog Timer
Rev.6.00 Sep. 27, 2007 Page 581 of 1268
REJ09B0220-0600
Section 13 Watchdog Timer
13.1 Overview
The chip 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 chip.
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.
13.1.1 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 chip is reset at the same time
• Interrupt generation when in interval timer mode
If the counter overflows, the WDT generates an interval timer interrupt
• Choice of eight counter clock sources
Note: * The WDTOVF pin function cannot be used in the F-ZTAT versions.