Abstract: An EEPROM system with an error detecting function includes: a memory cell matrix composed of a plurality of MOS memory cells and a plurality of bit lines connected separately to the plurality of MOS memory cells; and a plurality of intermediate state detecting circuits connected separately to the plurality of bit lines for detecting an intermediate state other than writing and erasing states of the MOS memory cells, and for outputting an error bit indicating signal, the intermediate state being a threshold voltage between a threshold voltage of a storage MOS memory cell in a writing state included in each of the MOS memory cells and a threshold voltage of the storage MOS memory cell in an erasing state.

Abstract: In a nonvolatile memory device or a microcomputer with a nonvolatile memory, data errors arising from loss of charge in the floating gates of memory cells are detected and corrected by applying two different sense voltages to the memory cells and comparing the outputs. Instead of using a cumbersome error-correcting code, this error-correcting scheme requires only one parity bit per word, yet it can detect and correct errors in any odd number of bits. Benefits include reduced chip size and longer life for electrically erasable and programmable memories.

Abstract: In IC card with a built-in IC, comprising an external power supply terminal and a solar battery, the external power supply terminal is connected to an IC internal power supply line through a first switch, the solar battery is connected to the IC internal power supply line through a second switch, and a voltage detection circuit is connected to the external power supply terminal. When the voltage detection circuit detects a voltage on the external power supply terminal, it switches ON the first switch and switches OFF the second switch. When it does not detect a voltage on the external power supply terminal it switches OFF the first switch and switches ON the second switch.

Abstract: An IC card having a plastics card body which mounts a CPU, a RAM, a ROM, a solar battery mounts also to EEPROM (electrically erasable programmable read only memory), which is used for identification of a card owner. Due to high power consumption of said EEPROM, a tandem type solar battery in which a plurality of opto-electric conversion cells are laminated on a substrate is used. The present IC card can operate with only the solar battery mounted inside of the IC card, and has no secondary battery.