The normal wake-up time for the device is 6 Main Clock cycles (CLK_PER),
plus the time it takes to start up the Main Clock source:
- In Idle sleep mode the Main Clock
source is kept running so it will not be any extra wake-up time.
- In Standby sleep mode the Main
Clock might be running, so it depends on the peripheral configuration.
- In Power Down sleep mode only the
ULP 32KHz oscillator and RTC clock may be running, if it is used by the BOD or
WDT. All other clock sources will be off.
Table 1. Sleep modes and Start-up time
| Sleep mode |
Start-up time |
| IDLE |
6 CLK |
| 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 net 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 is ensures correct supply voltage whenever
code is executed.