SH7108 Datasheet, PDF (305/560 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

Section 9 Watchdog Timer
Section 9 Watchdog Timer
This watchdog timer (WDT) module provides a single, 8-bit timer that can be used to monitor the
system. When the counter value is not rewritten due to a system crash (such as an infinite loop)
and the counter overflows, an overflow signal (WDTOVF) is output to external circuits. It is also
possible to issue an IC internal reset signal at the same time.
If this module is not used as a watchdog timer, it can be used as an interval timer. If it is used as an
interval timer, the interval timer interrupt (ITI) will be generated each time the counter overflows.
The watchdog timer can also be used when standby mode is cleared. Figure 9.1 shows the block
timer of the WDT module.
The block diagram of the WDT is shown in figure 9.1.
9.1 Features
• Selectable from eight counter input clocks
• Switchable between watchdog timer mode and interval timer mode
• Used to clear software standby mode
In watchdog timer mode
• Output WDTOVF signal
• If the counter overflows, it is possible to select whether this LSI is internally reset or not.
In interval timer mode
• If the counter overflows, the WDT generates an interval timer interrupt (ITI).
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Rev.1.00 Sep. 18, 2008 Page 271 of 522
REJ09B0069-0100