Do you have "EFM32 Cortex-M4 Reference Manual" document file?
efm32pg1_reference_manual document mention about it. but I not find it.
You need to get core-specific documentation from ARM.
Google is your friend:
I agree with John, though we have a RM for M3 MCU but it looks like there is no one for M4.
Our Cortex-M3 manual is just a rehash of the ARM document for the M3 in the original Energy Micro formatting and colors. Other than listing which versions of the M3 we used on the different Series 0 devices, I don't think we presented any information that was different from what ARM has in the original document. Of course, I didn't quite have the time to read the whole thing