HD6417021 Hitachi Semiconductor, HD6417021 Datasheet - Page 352

• Manufacturer Part Number: HD6417021
• Description: SuperH RISC engine
• Manufacturer: Hitachi Semiconductor

12.4
12.4.1
If a timer counter clock pulse is generated during the T3 state of a write cycle to the TCNT, the
write takes priority and the timer counter is not incremented (figure 12.8).
12.4.2
If the values of bits CKS2–CKS0 are altered while the WDT is running, the count may increment
incorrectly. Always stop the watchdog timer (by clearing the TME bit to 0) before changing the
values of bits CKS2–CKS0.
12.4.3
To prevent incorrect operation, always stop the watchdog timer (by clearing the TME bit to 0)
before switching between interval timer mode and watchdog timer mode.
HITACHI 338
Usage Notes
TCNT Write and Count Up Contention
Changing CKS2-CKS0 Bit Values
Changing Watchdog Timer/Interval Timer Modes
write signal
input clock
Address
Internal
Figure 12.8 Contention between TCNT Write and Increment
TCNT
TCNT
CK
T1
TCNT write cycle
TCNT address
N
T2
Counter write data
T3
M