Section 13 Watchdog Timer (WDT)
Rev. 2.00 Mar 09, 2006 page 552 of 906
REJ09B0292-0200
13.3.2
Operation in Interval Timer Mode
To use the WDT as an interval timer, clear WT/
IT
to 0 and set TME to 1 in WTCSR. An interval
timer interrupt (ITI) is generated each time the watchdog timer counter (WTCNT) overflows. This
function can be used to generate interval timer interrupts at regular intervals (figure 13.5).
ITI
ITI
ITI
ITI
WTCNT value
Overflow
Overflow
Overflow
Overflow
WT/
IT
= 0
TME = 1
H'FF
H'00
Time
ITI: Interval timer interrupt request generation
Figure 13.5 Operation in Interval Timer Mode
13.3.3
Operation when Standby Mode is Cleared
The watchdog timer has a special function to clear standby mode with an NMI interrupt. When
using standby mode, set the WDT as described below.
Transition to Standby Mode:
The TME bit in WTCSR must be cleared to 0 to stop the watchdog
timer counter before it enters standby mode. The chip cannot enter standby mode while the TME
bit is set to 1. Set bits CKS2 to CKS0 in WTCSR so that the counter overflow interval is equal to
or longer than the oscillation settling time. See section 22, Electrical Characteristics, for the
oscillation settling time.
Recovery from Standby Mode:
When an NMI request signal is received in standby mode the
clock oscillator starts running and the watchdog timer starts counting at the rate selected by bits
CKS2 to CKS0 before standby mode was entered. When WTCNT overflows (changes from H'FF
to H'00) the system clock (
φ
) is presumed to be stable and usable; clock signals are supplied to the
entire chip and standby mode ends.
For details on standby mode, see section 21, Power Down Modes.
Содержание SH7616
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Страница 132: ...Section 2 CPU Rev 2 00 Mar 09 2006 page 106 of 906 REJ09B0292 0200 ...
Страница 568: ...Section 12 16 Bit Free Running Timer FRT Rev 2 00 Mar 09 2006 page 542 of 906 REJ09B0292 0200 ...
Страница 582: ...Section 13 Watchdog Timer WDT Rev 2 00 Mar 09 2006 page 556 of 906 REJ09B0292 0200 ...
Страница 662: ...Section 14 Serial Communication Interface with FIFO SCIF Rev 2 00 Mar 09 2006 page 636 of 906 REJ09B0292 0200 ...
Страница 706: ...Section 16 Serial I O SIO Rev 2 00 Mar 09 2006 page 680 of 906 REJ09B0292 0200 ...
Страница 820: ...Section 19 Pin Function Controller PFC Rev 2 00 Mar 09 2006 page 794 of 906 REJ09B0292 0200 ...
Страница 932: ...Appendix D Package Dimensions Rev 2 00 Mar 09 2006 page 906 of 906 REJ09B0292 0200 ...
Страница 935: ...SH7616 Hardware Manual ...