Wake-up Time

The normal wake-up time for the device is six main clock cycles (CLK_PER), plus the time it takes to start the main clock source:
Table 1. Sleep Modes and Start-up Time
Sleep Mode Start-up Time
Standby 6 CLK + OSC start-up
Power-Down 6 CLK + OSC start-up
The start-up time for the different clock sources is described in the Clock Controller (CLKCTRL) section.

In addition to the normal wake-up time, it is possible to make the device wait until the BOD is ready before executing code. This is done by writing 0x3 to the BOD Operation mode in Active and Idle bits (ACTIVE) in the BOD Configuration fuse (FUSE.BODCFG). If the BOD is ready before the normal wake-up time, the total wake-up time will be the same. If the BOD takes longer than the normal wake-up time, the wake-up time will be extended until the BOD is ready. This ensures correct supply voltage whenever code is executed.