Datasheet

Table Of Contents
Section 12 Watchdog Timer (WDT)
Page 378 of 846 REJ09B0140-0900 Rev. 9.00
Sep 16, 2010
H8S/2215 Group
12.5.2 Contention between Timer Counter (TCNT) Write and Increment
If a timer counter clock pulse is generated during the T
2
state of a TCNT write cycle, the write
takes priority and the timer counter is not incremented. Figure 12.8 shows this operation.
Address
φ
Internal write
signal
TCNT input
clock
TCNT
NM
T
1
T
2
TCNT write cycle
Counter write data
Figure 12.8 Contention between TCNT Write and Increment
12.5.3 Changing Value of CKS2 to CKS0
If bits CKS0 to CKS2 in TCSR are written to while the WDT is operating, errors could occur in
the incrementation. Software must be used to stop the watchdog timer (by clearing the TME bit to
0) before changing the value of bits CKS0 to CKS2.
12.5.4 Switching between Watchdog Timer Mode and Interval Timer Mode
If the mode is switched from watchdog timer to interval timer while the WDT is operating, errors
could occur in the incrementation. Software must be used to stop the watchdog timer (by clearing
the TME bit to 0) before switching the mode.