Section 12
Watchdog Timer (WDT)
Rev.2.00 Jun. 28, 2007 Page 447 of 666
REJ09B0311-0200
12.6.5
Internal Reset in Watchdog Timer Mode
This LSI is not reset internally if TCNT overflows while the RSTE bit is cleared to 0 during
watchdog timer mode operation, but TCNT and TCSR 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 TCSR after the
WDTOVF
signal goes high, and then write 0 to the WOVF flag.
12.6.6
System Reset by
WDTOVF
Signal
If the
WDTOVF
signal is input to the
RES
pin, this LSI 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 a circuit like that shown in figure 12.6.
Reset input
Reset signal to entire system
This LSI
RES
WDTOVF
Figure 12.6 Circuit for System Reset by
WDTOVF
Signal (Example)
12.6.7
Transition to Watchdog Timer Mode or Software Standby Mode
When the WDT operates in watchdog timer mode, a transition to software standby mode is not
made even when the SLEEP instruction is executed when the SSBY bit in SBYCR is set to 1.
Instead, a transition to sleep mode is made.
To transit to software standby mode, the SLEEP instruction must be executed after halting the
WDT (clearing the TME bit to 0).
When the WDT operates in interval timer mode, a transition to software standby mode is made
through execution of the SLEEP instruction when the SSBY bit in SBYCR is set to 1.
Summary of Contents for H8SX/1650
Page 2: ...Rev 2 00 Jun 28 2007 Page ii of xxii...
Page 106: ...Section 4 Exception Handling Rev 2 00 Jun 28 2007 Page 84 of 666 REJ09B0311 0200...
Page 142: ...Section 5 Interrupt Controller Rev 2 00 Jun 28 2007 Page 120 of 666 REJ09B0311 0200...
Page 326: ...Section 8 I O Ports Rev 2 00 Jun 28 2007 Page 304 of 666 REJ09B0311 0200...
Page 470: ...Section 12 Watchdog Timer WDT Rev 2 00 Jun 28 2007 Page 448 of 666 REJ09B0311 0200...
Page 566: ...Section 14 A D Converter Rev 2 00 Jun 28 2007 Page 544 of 666 REJ09B0311 0200...
Page 574: ...Section 16 RAM Rev 2 00 Jun 28 2007 Page 552 of 666 REJ09B0311 0200...
Page 584: ...Section 17 Clock Pulse Generator Rev 2 00 Jun 28 2007 Page 562 of 666 REJ09B0311 0200...
Page 638: ...Section 19 List of Registers Rev 2 00 Jun 28 2007 Page 616 of 666 REJ09B0311 0200...
Page 668: ...Section 20 Electrical Characteristics Rev 2 00 Jun 28 2007 Page 646 of 666 REJ09B0311 0200...
Page 676: ...Appendix Rev 2 00 Jun 28 2007 Page 654 of 666 REJ09B0311 0200...
Page 688: ...Rev 2 00 Jun 28 2007 Page 666 of 666 REJ09B0311 0200...
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Page 692: ...H8SX 1650 Group Hardware Manual...