30.6.4 Command and Data Interface

The NVM Controller is addressable from the APB bus, while the NVM main address space is addressable from the AHB bus. Read and automatic page write operations are performed by addressing the FLASH, Data FLASH and NVM Rows arrays directly, while other operations such as manual page writes and row erases must be performed by issuing commands through the NVM Controller.

To issue a command, the CTRLA.CMD bits must be written along with the CTRLA.CMDEX value. When a command is issued, STATUS.READY is cleared and rises again when the command has completed. INTFLAG.DONE is also set when a command completes. Any commands written while INTFLAG.READY is low will be ignored.

The CTRLB and CTRLC registers must be used to control the power reduction mode, read wait states, and the write mode.