atmega161-4pi ATMEL Corporation, atmega161-4pi Datasheet - Page 59

• Manufacturer Part Number: atmega161-4pi
• Description: 8-bit Microcontroller With 16k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

1228D–AVR–02/07
WDTOE bit is set (one). To disable an enabled Watchdog Timer, the following proce-
dure must be followed:
1. In the same operation, write a logical “1” to WDTOE and WDE. A logical “1” must
2. Within the next four clock cycles, write a logical “0” to WDE. This disables the
• Bits 2..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
time-out periods are shown in Table 20.
Table 20. Watchdog Timer Prescale Select
Note:
WDP2
0
0
0
0
1
1
1
1
be written to WDE even though it is set to one before the disable operation starts.
Watchdog.
1. The frequency of the Watchdog Oscillator is voltage-dependent, as shown in the
WDP1
Electrical Characteristics section.
The WDR (Watchdog Reset) instruction should always be executed before the
Watchdog Timer is enabled. This ensures that the reset period will be in accordance
with the Watchdog Timer prescale settings. If the Watchdog Timer is enabled without
reset, the Watchdog Timer may not start counting from zero.
To avoid unintentional MCU Reset, the Watchdog Timer should be disabled or reset
before changing the Watchdog Timer Prescale Select.
–
0
0
1
1
0
0
1
1
WDP2, WDP1, WDP0: Watchdog Timer Prescaler 2, 1 and 0
WDP0
0
1
0
1
0
1
0
1
Oscillator Cycles
Number of WDT
1,024K
2,048K
128K
256K
512K
16K
32K
64K
(1)
Typical Time-out
at V
47 ms
94 ms
0.19 s
0.38 s
0.75 s
CC
1.5 s
3.0 s
6.0 s
= 3.0V
ATmega161(L)
Typical Time-out
at V
15 ms
30 ms
60 ms
0.12 s
0.24 s
0.49 s
0.97 s
CC
1.9 s
= 5.0V
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