RTC not active in simulated power down mode

I am simulating a power down condition in uVision using LPC2138.
The problem is that the RTC (real time clock) is halting when the processor is in the power down mode.
The RTC is using an external clock source 38 Khz and should be active. I want to use the RTC to wake up the processor.

Another problem is that the RTC with external clock is not working when the internal power is off (PCONPB.PCRTC = 0). It should, because the power is now coming from pin nr. 49, Vbat.

Any solutions to this?

Thanks,
Petter Gran-Janssen