Datasheet

Section 12 Watchdog Timer (WDT)
Rev. 3.00 Sep. 28, 2009 Page 235 of 710
REJ09B0384-0300
Section 12 Watchdog Timer (WDT)
This LSI has two watchdog timer channels (WDT_0 and WDT_1). The watchdog timer can output
an overflow signal (RESO) externally if a system crash prevents the CPU from writing to the
timer counter, thus allowing it to overflow. Simultaneously, it can generate an internal reset signal
or an internal NMI interrupt signal.
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. A block
diagram of the WDT_0 and WDT_1 are shown in figure 12.1.
12.1 Features
• Selectable from eight (WDT_0) or 16 (WDT_1) counter input clocks.
• Switchable between watchdog timer mode and interval timer mode
Watchdog Timer Mode:
• If the counter overflows, an internal reset or an internal NMI interrupt is generated.
• When the LSI is selected to be internally reset at counter overflow, a low level signal is output
from the RESO pin if the counter overflows.
Internal Timer Mode:
• If the counter overflows, an internal timer interrupt (WOVI) is generated.