ATMEga64L ATMEL Corporation, ATMEga64L Datasheet - Page 56

• Manufacturer Part Number: ATMEga64L
• Description: 8-bit AVR Microcontroller with 64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

56
ATmega64(L)
• 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 58.
• 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 22.
Table 22. Watchdog Timer Prescale Select
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.
WDP1
0
0
1
1
0
0
1
1
WDP0
0
1
0
1
0
1
0
1
1,024K (1,048,576)
2,048K (2,097,152)
Oscillator Cycles
Number of WDT
128K (131,072)
256K (262,144)
512K (524,288)
16K (16,384)
32K (32,768)
64K (65,536)
Typical Time-out
at V
17.1 ms
34.3 ms
68.5 ms
0.14 s
0.27 s
0.55 s
CC
1.1 s
2.2 s
= 3.0V
Typical Time-out
at V
2490G–AVR–03/04
32.5 ms
16.3 ms
65 ms
0.13 s
0.26 s
0.52 s
CC
1.0 s
2.1 s
= 5.0V