D12320VF25IV Datasheet, PDF (627/1304 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 13 Watchdog Timer
13.5.2 Changing Value of CKS2 to CKS0
If bits CKS2 to CKS0 in TCSR are written to while the WDT is operating, errors may occur in the
incrementation. Software must stop the watchdog timer (by clearing the TME bit to 0) before
changing the value of bits CKS2 to CKS0.
13.5.3 Switching between Watchdog Timer Mode and Interval Timer Mode
If the mode is switched from watchdog timer to interval timer, or vice versa, while the WDT is
operating, errors may occur in the incrementation. Software must stop the watchdog timer (by
clearing the TME bit to 0) before switching the mode.
13.5.4 System Reset by WDTOVF Signal^*
If the WDTOVF output signal* is input to the RES pin of the chip, the chip will not be initialized
correctly. Make sure that the WDTOVF signal* is not input logically to the RES pin. To reset the
entire system by means of the WDTOVF signal*, use the circuit shown in figure 13.9.
Note: * The WDTOVF pin function cannot be used in the F-ZTAT versions.
Reset input
Chip
RES
Reset signal to entire system
WDTOVF^*
Note: * The WDTOVF pin function cannot be used in the F-ZTAT versions.
Figure 13.9 Circuit for System Reset by WDTOVF Signal (Example)
Rev.6.00 Sep. 27, 2007 Page 595 of 1268
REJ09B0220-0600