Renesas H8S/2318 series, Hardware Manual

Page: 450 / 1121

Rev. 5.00, 12/03, page 420 of 1088
11.5.4 System Reset by
WDTOVF
WDTOVF WDTOVF
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 11-9.
Note: * The
WDTOVF
output function is not available in the F-ZTAT versions.
Reset input
Reset signal to entire system
Chip
RES
WDTOVF
*
Note:
*
The
WDTOVF
output function is not available in F-ZTAT versions.
Figure 11-9 Circuit for System Reset by
WDTOVF
WDTOVF WDTOVF
WDTOVF
Signal (Example)
11.5.5 Internal Reset in Watchdog Timer Mode
The chip is not reset internally if TCNT overflows while the RSTE bit is cleared to 0 during
watchdog timer operation, but TCNT and TSCR of the WDT are reset.
TCNT, TCSR, and RSTCR cannot be written to while the
WDTOVF
signal* is low. Also note that
a read of the WOVF flag is not recognized during this period. To clear the WOVF flag, therefore,
read RSTCSR after the
WDTOVF
signal* goes high, then write 0 to the WOVF flag.
Note: * The
WDTOVF
output function is not available in the F-ZTAT versions.