Abstract: A semiconductor storage device having a semiconductor memory for storing various data, a connector portion for uniting with a reader-writer device, and a memory control portion for controlling reading of data from the semiconductor memory and writing of data into the semiconductor memory in accordance with an instruction from the reader-writer device inputted through the connector portion. The semiconductor memory has a set password storage region where a set password has been written. The device is provided with a set password address comparison portion for outputting a coincidence signal to the memory control portion when an address signal inputted from the connector portion points to the set password storage region and a password collation portion for outputting a coincidence signal to the memory control portion when the set password outputted from the memory control portion and the input password inputted from the connector portion coincide with each other.

Abstract: A memory card and a data processing device for preventing erroneous writing operation to the memory card at the time of inserting into and pulling out from the data processing device. For the purpose of preventing the erroneous writing operation to the card at the time of inserting into the data processing device, an enable signal generating circuit of the memory card is arranged not to generate an enable signal in an unstable time period during which chattering takes place when the card starts receiving power from the external data processing device through a voltage detecting circuit of the card and the received power supply voltage reaches a predetermined level. For the purpose of preventing the erroneous writing operation to the card at the time of pulling out from the data processing device, a capacitor is connected between a power supply line of the card and the ground so that a chip select signal is maintained at high level until an enable signal becomes high level.

Abstract: A function of write protection against careless writing in a memory card is realized by means other than a mechanical switch. Existing address lines exceeding the capacity of a memory and an existing write control line are used as inputs to a gate circuit so that data can be written in the memory only in the case where a specific value can be decoded. Accordingly, a write address space is limited to a specific address space other than the lowermost address space. Accordingly, data cannot be written if the specific address space cannot be known. As a result, the function of write protection can be provided without using any switch and without introducing any nonstandardized terminal and any control signal.