Hi Eduardo
The CLKCON register is not related to the SLEEP timer in any way. If you look in the Sleep Timer Section of the data sheet you will see the following:
“Note: In this section of the document, fRef is used to denote the reference frequency for the synthesizer. For CC2510Fx fref = fXOSC”
This means that it is only WOR_RES and EVENT0 that sets the sleep interval.
You must also follow the SW work-around stated in the errata note to safely enter and exit PM2.
BR
Siri