Abstract: A controller 3 of a memory card is a provided with a command decoding circuit 6 for decoding commands issued by a host HT, a command enable register 8 in which the validity or invalidity of the received command, and a command detection signal generating circuit 7 for detecting a valid command on the basis of the result of decoding by the command decoding circuit 6 and a value set by the command enable register 8. If the command enable register 8 receives a validly set command, the command detection signal generating circuit 7 will supply a detection signal to a control unit 4 to execute processing prescribed for each command. the command enable register 8 receives an invalidly set command, no detection signal will be supplied, and the command will be ignored.

Abstract: A controller 3 of a memory card is a provided with a command decoding circuit 6 for decoding commands issued by a host HT, a command enable register 8 in which the validity or invalidity of the received command, and a command detection signal generating circuit 7 for detecting a valid command on the basis of the result of decoding by the command decoding circuit 6 and a value set by the command enable register 8. If the command enable register 8 receives a validly set command, the command detection signal generating circuit 7 will supply a detection signal to a control unit 4 to execute processing prescribed for each command. the command enable register 8 receives an invalidly set command, no detection signal will be supplied, and the command will be ignored.

Abstract: A controller 3 of a memory card is a provided with a command decoding circuit 6 for decoding commands issued by a host HT, a command enable register 8 in which the validity or invalidity of the received command, and a command detection signal generating circuit 7 for detecting a valid command on the basis of the result of decoding by the command decoding circuit 6 and a value set by the command enable register 8. If the command enable register 8 receives a validly set command, the command detection signal generating circuit 7 will supply a detection signal to a control unit 4 to execute processing prescribed for each command the command enable register 8 receives an invalidly set command, no detection signal will be supplied, and the command will be ignored.

Abstract: In a nonvolatile semiconductor memory device, a high voltage is selectively exerted between a word line to which the control gates of nonvolatile semiconductor memory elements are coupled and a source line to which the sources of the nonvolatile semiconductor memory elements are coupled, whereby charges stored in the floating gates are extracted through the source line. In addition, the nonvolatile semiconductor memory elements to be erased are provided with a source potential having ramp-rate characteristics such that the sources are gradually raised from a low voltage to the high voltage. Thus, the erasure of a predetermined part of the memory array of the memory device becomes possible in accordance with the division of the source lines or that of the word lines, and an excessive intense electric field can be prevented from acting between the floating gates and the sources because a ramp rate is used for the erasing high voltage.

Abstract: A time circuit is provided for a nonvolatile memory device which can electrically be written into. When the write operation on a particular memory cell lasting a relatively long period of time is specified from an external device, the memory device stops the write operation on that memory cell, irrespective of the external write operaiton specification, when the time set on the timer circuit has elapsed. The nonvolatile memory device has memory cells, each consisting of a single transistor. The erase operation on the memory cells is controlled according to a current flowing through these memory cells.