Help to wake up CC2538 chip (Contiki) from PM2/PM3 low power modes

Dear TI Engineers,

 I am using CC2538 (EM) over SmartRF06 Evaluation Board (EB). In order to measure current consumption during low power modes, I have put the CC2538 chip in the PM2 low power mode using the following two lines in my code.

lpm_enter();

REG(SYS_CTRL_PMCTL) = SYS_CTRL_PMCTL_PM2;

Is this the correct way to make the device to go to sleep/low power mode?

I now wish to wake up the CC2538 chip from this PM2 state after a delay of say 10 seconds and return to PM0 (active) state.

(In order to achieve this, I have tried lpm_exit(); and REG(SYS_CTRL_PMCTL) = SYS_CTRL_PMCTL_PM0; but with no success.)

Thanking you,

Indrajit