ATMEGA169 ATMEL [ATMEL Corporation], ATMEGA169 Datasheet - Page 44

• Manufacturer Part Number: ATMEGA169
• Description: 8-bit Microcontroller with 16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

44
ATmega169/V
• Bit 3 – WDE: Watchdog Enable
When the WDE is written to logic one, the Watchdog Timer is enabled, and if the WDE is
written to logic zero, the Watchdog Timer function is disabled. WDE can only be cleared
if the WDCE bit has logic level one. To disable an enabled Watchdog Timer, the follow-
ing procedure must be followed:
1. In the same operation, write a logic one to WDCE and WDE. A logic one must be
2. Within the next four clock cycles, write a logic 0 to WDE. This disables the
In safety level 2, it is not possible to disable the Watchdog Timer, even with the algo-
rithm described above. See “Timed Sequences for Changing the Configuration of the
Watchdog Timer” on page 45.
• Bits 2..0 – WDP2, WDP1, WDP0: Watchdog Timer Prescaler 2, 1, and 0
The WDP2, WDP1, and WDP0 bits determine the Watchdog Timer prescaling when the
Watchdog Timer is enabled. The different prescaling values and their corresponding
Timeout Periods are shown in Table 21.
Table 21. Watchdog Timer Prescale Select
Note:
WDP2
0
0
0
0
1
1
1
1
written to WDE even though it is set to one before the disable operation starts.
Watchdog.
Also see Figure 191 on page 332.
WDP1
0
0
1
1
0
0
1
1
WDP0
0
1
0
1
0
1
0
1
Oscillator Cycles
Number of WDT
1,024K cycles
2,048K cycles
128K cycles
256K cycles
512K cycles
16K cycles
32K cycles
64K cycles
Typical Time-out
at V
15.4 ms
30.8 ms
61.6 ms
0.12 s
0.25 s
0.49 s
CC
1.0 s
2.0 s
= 3.0V
Typical Time-out
at V
14.7 ms
29.3 ms
58.7 ms
2514P–AVR–07/06
0.12 s
0.23 s
0.47 s
CC
0.9 s
1.9 s
= 5.0V