An electrically erasable and programmable non-volatile semiconductor memory includes memory registers that are addressable individually or by blocks. The memory also has a protection register in which a protection word can be written. The protection word has a given number of bits that encode a boundary address of the memory register or a block of memory registers. The boundary address divides the memory space into an upper zone and a lower zone. The protection word also has a zone bit whose value determines which of the two zones of the memory is to be write protectable.