Memory system storing block protection information

A method of operating a memory system including a nonvolatile semiconductor memory having a plurality of blocks and an interface connected to a host, the interface including a first pin for a chip select signal and a second pin for a data signal, the method comprising:

• determining that the data signal received from the host through the second pin, immediately after the chip select signal is asserted on the first pin by the host is a block protection command;
• and
• in response to the block protection command, storing an indication that a particular block of the plurality of blocks is prohibited from writing or erasing.