JPS63271554A - Ic memory card - Google Patents

Abstract

PURPOSE:To easily provide a thin type IC memory card with a write protecting function by boring a small light-transmission window in the case of the IC memory card and providing a means which detects light passed through the small window and a means which prevents the IC memory card from being rewritten according to the detection result. CONSTITUTION:The small window 3 which passes light is bored in the case, which has the means for detecting the light passing through the small window 3 and the means for preventing the IC memory from being rewritten according to the detection result. Then a photodiode D1 is arranged, for example, right below the small window 3. When the small window 3 is irradiated with natural light, etc., the memory IC 4 can be written and read freely through an external R/W terminal and when a seal, etc., is stuck on the small window 3 to cut off the light the IC memory is protected from writing.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an IC memory card, and particularly relates to an IC memory card that is capable of preventing rewriting (hereinafter referred to as a write protect function).
Regarding C memory cards.

[Conventional technology]

Conventionally, this type of write protection function has been provided by a mechanical switch. FIG. 3 shows a conventional write protect circuit. SW is a mechanical switch, R4 is a resistor, and IC is a memory IC of an IC memory card. SW
The external B4 terminal and the real terminal of the IC are connected through the external B4 terminal, and writing/reading and write protection can be performed. R4 always holds the R/W terminal of the memory IC at a high level during write protection (when SW is off). Therefore, since the level of the external R/W terminal is irrelevant, write protection is possible.

[Problem that the invention seeks to solve]

In a thin card having a thickness of IW or less, it is difficult to incorporate a mechanical switch used for the write protection function into the card. In addition, poor contact with the switch is likely to occur.

In view of the above circumstances, it is an object of the present invention to provide a thin I/O device having a novel write protection function without using a mechanical switch.
C memory card.

[Means for solving problems]

The IC memory card of the present invention has a light-transmitting small window provided in the case, means for detecting light transmitted through the small window, and means for preventing rewriting of the IC memory based on the detection result. This is how it was done.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. Figure 1(a) is a card outline diagram of the example, Figure 1(b)
is a circuit that implements the write protection function. l is I
C memory card, 2 is a card external terminal, and 3 is a small translucent window. The small window 3 is a part of the case made of glass or plastic. A photodiode D1 shown in FIG. 1(b) is placed directly under the small window 3. In the embodiment, when the small window 3 is illuminated with natural light, it is possible to freely write to and read from the mesori IC 4 from the external R/W terminal, and a 7-ru or the like is pasted on the small window 3. It is light protected by blocking light.

FIG. 1(b) is a write protect circuit, in which the external R
An analog switch 5 is provided between the /W terminal and the memory IC 40R/W terminal. The analog switch 5 is
Inverter 5&, N-channel MO8) transistor 5b,
A well-known switch consisting of a P-channel MOS transistor 5C is controlled to be turned on when the potential at the node N between the photodiode DI and the resistor R1 is at a high level, and turned off when it is at a low level. Therefore, when light is incident from the small window 3, the photodiode D1 is not conductive and the node N is at a high level, so the analog switch 5 is not on and writing/reading from the external R/W terminal is not possible. It is possible. When no light enters from the small window 3, the node N is at low level] and the analog switch 5 is turned off. Memo!
The R/v terminal of the JIC4 is always at a high level due to the pull-up resistor R2, and is independent of the level of the external R/W terminal. Regarding the above, the small window 3t of IC memory card 1
- You can write protect it by pasting a sticker on it.

As an application of the IC memory card of the present invention, a case will be described in which a light emitting diode is provided on the IC memory card insertion device side so that the write protect function can be canceled more reliably than in the case of natural light. That is, when the light transmittance of the small window 3 is weakened so that natural light is always protected from light, and when the light emitting diode D2 provided in the device is made to emit light as shown in FIG. Remove write protection.

After inserting the IC memory card 1, a voltage is applied to the light emitting diode D2 (by a switch (not shown)) to release the write protection and write/read data is performed.

〔Effect of the invention〕

As described above, since the present invention does not use a mechanical switch to provide the write protection function, it is possible to easily provide the write protection function to a thin IC memory card.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, and FIG. 3 shows a conventional example. 1...IC memory card, 3...external terminal, 4...memory IC. 5...Analog switch.

Claims (1)

[Claims] A small translucent window is installed in the IC memory card case.
An IC memory card comprising means for detecting light transmitted through the small window, and means for preventing rewriting of the IC memory based on the detection result.