Hello,

I have a custom board populated with the AT91SAM9263 and I get boot problems when I turn off the board and turn it on after less than around 10 seconds (if I wait more than 10 seconds, the device boots correctly). The boot process stops after the OEMInit (so that a lot of process/init have already been done successfully). The Debug messages appearing after that in case of successful boot are related to the RTC.
When turned off, the VDDBU is supplied with a 3V battery and a linear voltage regulator.

The DC voltages are good and goes back to GND in less than the 10 seconds.

The power up sequence seems good too.

Does anyone have an idea ?

calculate the capacitance value of capacitors mounted on your board , try to reduce capacitance from board.

You can also check the power down sequence:
Switch off the VDDIOM and VDDIOP power supplies prior to, or at the same time, as VDDCORE. No power-up or power-down restrictions apply to VDDBU, VDDPL, VDDANA and VDDUSB.

The solution:

VOID NKForceCleanBoot(void);
Parameters
None.

Return Values
None.

Remarks
The hardware on some devices accidentally preserves RAM contents after brief power losses due to capacitance.

Unless these devices are intentionally preserving RAM contents using self-refresh, these devices should always call NKForceCleanBoot so the object store does not appear valid at boot time. Otherwise, devices are likely to experience crash problems during boot.