US 5,517,460 AGranted

Semiconductor integrated circuit and IC card using the same

AssigneeMitsubishi Denki Kabushiki Kaisha

InventorAtsuo Yamaguchi

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Abstract

A semiconductor integrated circuit includes: a writable non-volatile memory; a writing voltage-generating circuit for generating a writing voltage and supplying it to the non-volatile memory; an oscillating circuit for generating a first clock signal and supplying it to the writing voltage-generating circuit; a timer for measuring a time the writing voltage generated in the writing voltage-generating circuit is applied to the non-volatile memory; a control circuit for controlling writing in the non-volatile memory; and a switching device for selecting one of the first clock signal generated in the oscillating circuit and a second clock signal input from outside the integrated circuit in response to a control signal from the control circuit, thereby supplying the selected signal to the timer and the control circuit as a clock.

Claims10

Dependent claims

A semiconductor integrated circuit comprising:

a non-volatile memory for storing stored data, from which stored data can be erased, and from which stored data may be read;
a writing voltage-generating circuit for generating a writing voltage and supplying the writing voltage to said non-volatile memory for storing data in said non-volatile memory;
an oscillating circuit, including a clock signal-generating circuit and an oscillation circuit, for generating a first clock signal and supplying the first clock signal to said writing voltage-generating circuit;
a timer for measuring duration of application of the writing voltage generated in said writing voltage-generating circuit to said non-volatile memory;
a control circuit for controlling storing of data in said non-volatile memory;
and
switching means for selecting one of the first clock signal generated in said oscillating circuit and a second, external clock signal input to said semiconductor integrated circuit in response to a control signal supplied to said switching means by said control circuit, thereby supplying the selected one of the first and second clock signals to said timer and said control circuit as a clock.

4 more elements

An IC card comprising:

a central processing unit (CPU) for processing data in response to a second clock signal;
a read only memory (ROM) storing a program for operating said CPU;
a random access memory (RAM) for temporarily storing data;
an input/output circuit for data communication with an external unit;
a non-volatile memory for storing stored data, from which stored data can be erased, and from which stored data may be read;
a writing voltage-generating circuit for generating a writing voltage and supplying the writing voltage to said non-volatile memory for storing data in said non-volatile memory;
an oscillating circuit, including a clock signal-generating circuit and an oscillation circuit, for generating a first clock signal and supplying the first clock signal to said writing voltage-generating circuit;
a timer for measuring duration of application of the writing voltage generated in said writing voltage-generating circuit to said non-volatile memory;
a control circuit for controlling storing of data in said non-volatile memory;
and
switching means for selecting one of the first clock signal generated in said oscillating circuit and a second, external clock signal input supplied to said switching means by said CPU in response to a control signal from said control circuit, thereby supplying the selected one of the first and second clock signals to said timer and said control circuit as a clock.

8 more elements

Dependencies are inferred from the claim text.