9.3.2.4.2 Erase Page Command
The Erase Page (ER) command erases the current page. There must be one byte written in the page buffer for the Erase Page (ER) command to take effect.
For erasing the Flash, first, write to one address on the desired page, then execute the command. The whole page in the Flash will then be erased. The CPU will be halted while the erase is ongoing.
For the EEPROM, only the bytes written in the page buffer will be erased when the command is executed. To erase a specific byte, write to its corresponding address before executing the command. To erase a whole page, all the bytes in the page buffer have to be updated before executing the command. The CPU can continue running code while the operation is ongoing.
The page buffer will automatically be cleared after the operation is finished.