Section 13 Watchdog Timer (WDT)
Rev. 2.00 Mar 09, 2006 page 550 of 906
REJ09B0292-0200
Writing 0 to the WOVF bit
15
8 7
0
Address:
H'FFFFFE82
H'A5
H'00
Writing to the RSTE and RSTS bits
15
8 7
0
Address:
H'FFFFFE82
H'5A
Write data
Figure 13.3 Writing to RSTCSR
Reading from WTCNT, WTCSR, and RSTCSR:
WTCNT, WTCSR, and RSTCSR are read
like other registers. Use byte transfer instructions. The read addresses are H'FFFFFE80 for
WTCSR, H'FFFFFE81 for WTCNT, and H'FFFFFE83 for RSTCSR.
13.3
Operation
13.3.1
Operation in Watchdog Timer Mode
To use the WDT as a watchdog timer, set the WT/
IT
and TME bits in WTCSR to 1. Software
must prevent WTCNT overflow by rewriting the WTCNT value (normally by writing H'00) before
overflow occurs. Thus, WTCNT will not overflow while the system is operating normally, but if
WTCNT fails to be rewritten and overflows occur due to a system crash or the like, a
WDTOVF
signal is output (figure 13.4). The
WDTOVF
signal can be used to reset the system. The
WDTOVF
signal is output for 512
φ
clock cycles.
If the RSTE bit in RSTCSR is set to 1, a signal to reset the chip will be generated internally
simultaneously with the
WDTOVF
signal when WTCNT overflows. Either a power-on reset or a
manual reset can be selected by the RSTS bit. The internal reset signal is output for 2048
φ
clock
cycles.
If a reset due to the input signal from the
RES
pin and a reset due to WDT overflow occur
simultaneously, the
RES
reset takes priority and the WOVF bit in RSTCSR is cleared to 0.
Summary of Contents for SH7616
Page 10: ...Rev 2 00 Mar 09 2006 page x of xxvi ...
Page 132: ...Section 2 CPU Rev 2 00 Mar 09 2006 page 106 of 906 REJ09B0292 0200 ...
Page 568: ...Section 12 16 Bit Free Running Timer FRT Rev 2 00 Mar 09 2006 page 542 of 906 REJ09B0292 0200 ...
Page 582: ...Section 13 Watchdog Timer WDT Rev 2 00 Mar 09 2006 page 556 of 906 REJ09B0292 0200 ...
Page 706: ...Section 16 Serial I O SIO Rev 2 00 Mar 09 2006 page 680 of 906 REJ09B0292 0200 ...
Page 820: ...Section 19 Pin Function Controller PFC Rev 2 00 Mar 09 2006 page 794 of 906 REJ09B0292 0200 ...
Page 932: ...Appendix D Package Dimensions Rev 2 00 Mar 09 2006 page 906 of 906 REJ09B0292 0200 ...
Page 935: ...SH7616 Hardware Manual ...