Datasheet

Bit 3 – WDE Watchdog System Reset Enable
WDE is overridden by WDRF in MCUSR. This means that WDE is always set when WDRF is set. To
clear WDE, WDRF must be cleared first. This feature ensures multiple resets during conditions causing
failure, and a safe start-up after the failure.
Bits 2:0 – WDP[2:0] Watchdog Timer Prescaler 2, 1, and 0
The WDP[3:0] bits determine the Watchdog Timer prescaling when the Watchdog Timer is running. The
different prescaling values and their corresponding time out periods are shown in the following table.
Table 15-2. Watchdog Timer Prescale Select
WDP[3] WDP[2] WDP[1] WDP[0] Number of WDT Oscillator (Cycles) Oscillator
0 0 0 0 2K (2048) 16 ms
0 0 0 1 4K (4096) 32 ms
0 0 1 0 8K (8192) 64 ms
0 0 1 1 16K (16384) 0.125s
0 1 0 0 32K (32768) 0.25s
0 1 0 1 64K (65536) 0.5s
0 1 1 0 128K (131072) 1.0s
0 1 1 1 256K (262144) 2.0s
1 0 0 0 512K (524288) 4.0s
1 0 0 1 1024K (1048576) 8.0s
1 0 1 0 Reserved
1 0 1 1
1 1 0 0
1 1 0 1
1 1 1 0
1 1 1 1
ATmega48PA/88PA/168PA
System Control and Reset
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40002011A-page 87