ATmega325PA Atmel Corporation, ATmega325PA Datasheet - Page 51

• Manufacturer Part Number: ATmega325PA
• Manufacturer: Atmel Corporation

11.4.1
11.4.1.1
11.4.1.2
8285D–AVR–06/11
Timed Sequences for Changing the Configuration of the Watchdog Timer
Safety Level 1
Safety Level 2
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
Figure 11-7. Watchdog Timer
The sequence for changing configuration differs slightly between the two safety levels. Separate
procedures are described for each level.
In this mode, the Watchdog Timer is initially disabled, but can be enabled by writing the WDE bit
to 1 without any restriction. A timed sequence is needed when changing the Watchdog Time-out
period or disabling an enabled Watchdog Timer. To disable an enabled Watchdog Timer, and/or
changing the Watchdog Time-out, the following procedure must be followed:
1. In the same operation, write a logic one to WDCE and WDE. A logic one must be written
2. Within the next four clock cycles, in the same operation, write the WDE and WDP bits as
In this mode, the Watchdog Timer is always enabled, and the WDE bit will always read as one. A
timed sequence is needed when changing the Watchdog Time-out period. To change the
Watchdog Time-out, the following procedure must be followed:
1. In the same operation, write a logical one to WDCE and WDE. Even though the WDE
Within the next four clock cycles, in the same operation, write the WDP bits as desired, but with
the WDCE bit cleared. The value written to the WDE bit is irrelevant.
to WDE regardless of the previous value of the WDE bit.
desired, but with the WDCE bit cleared.
always is set, the WDE must be written to one to start the timed sequence.
OSCILLATOR
WATCHDOG
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