A little background:
I have a CC1101 that has been working well. Occasionally though, it would stop receiving, and not reboot until the device was reset. I traced it down to the fact that occasionally, the CC1101 would lose PLL Lock, indicated by a 0x3F at the FSCAL1 register. I am using auto-calibration (FSCAL=0x01) which means I know at some point soon I will have to implement a handler that will detect the condition and cause the firmware to recalibrate the CC1101.
The strange part is that I have earlier versions of our firmware that I have never (to my knowledge) caused this PLL Lock issue. Nothing in the old firmware sets the registers of the CC1101 any differently then I do now, and there are no significant changes to the code that deals with the CC1101.
Here is my question: Is a change in temperature and voltage the *only* thing that can cause the PLL not to lock? For instance, can the frequency at which I send commands to the radio cause the PLL not to lock more often?