22.6.4.3.1 Procedure for Manual Page Writes (CTRLB.MANW=1)
The row to be written to must be erased before the write command is given.
- Write to the page buffer by addressing the NVM main address space directly
- Write the page buffer to memory: CTRL.CMD='Write Page' and CMDEX
- The READY bit in the INTFLAG register will be low while programming is in progress, and access through the AHB will be stalled