SH7108 Datasheet, PDF (311/560 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

TCNT value
H'FF
Overflow
Section 9 Watchdog Timer
H'00
WT/IT = 1 H'00 written
TME = 1 in TCNT
Time
WOVF = 1 WT/IT = 1
TME = 1
WDTOVF and internal
reset generated
H'00 written
in TCNT
WDTOVF
signal
Internal reset
signal*
WT/IT: Timer mode select bit
TME: Timer enable bit
128 φ clocks
512 φ clocks
Note: * Internal reset signal occurs only when the RSTE bit is set to 1.
Figure 9.2 Operation in Watchdog Timer Mode
9.4.2 Interval Timer Mode
To use the WDT as an interval timer, clear WT/IT to 0 and set TME to 1 in TCSR. An interval
timer interrupt (ITI) is generated each time the timer counter (TCNT) overflows. This function can
be used to generate interval timer interrupts at regular intervals.
TCNT value
H'FF
Overflow
Overflow
Overflow Overflow
H'00
WT/ = 0
ITI
ITI
ITI
ITI
TME = 1
ITI: Interval timer interrupt request generation
Figure 9.3 Operation in Interval Timer Mode
Time
Rev.1.00 Sep. 18, 2008 Page 277 of 522
REJ09B0069-0100