JPH02259853A - Input protecting method for memory card - Google Patents

Abstract

PURPOSE:To prevent a memory card from being unexpectedly destroyed by a read/writer by inserting a constant voltage diode and a resistor to an input circuit. CONSTITUTION:When an EPROM programmer is used as the reader/writer of the memory card, the EPROM programmer tries to obtain the identification information of the card by an ID code and the voltage signal of 1.25V is impressed to one terminal A9 in an address line 2. However, the voltage >=5V is not impressed to the input of the A9 in an address buffer 5 by the operation of a constant voltage diode 7 (a rated value is 5V). Thus, generally, the memory card is destroyed when the voltage more than the voltage of a power source is impressed to a semiconductor storing element and the respective input terminals of a semiconductor for interface. However, at the time of writing and reading of the memory card, the electric destruction can be prevented.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides information writing and reading equipment @ (hereinafter referred to as R /
This is related to the prevention of destruction of memory cards due to the careless application of electric signals from the W device.

[Prior art]

FIG. 2 shows a circuit diagram of a conventional memory card. In the figure, (1a) to (1n) are semiconductor memory elements, (2) are address lines named AO to An+m, respectively, for the purpose of selecting semiconductor memory elements, and (3) are semiconductor memory elements (1
For a) to (1n), a control line instructs control of reading, writing, etc., (4) a relative line for storing stored information, (5) an address buffer, and (6) an address decoder. The semiconductor memory elements (1a) to (1n) may not be of the same type. Further, the address buffer (5) is provided to improve electrical characteristics, and may be omitted depending on the case.

Next, a case where an EPROM programmer is used as an R/W device for writing and reading operations on a memory card using conventional technology will be described. The memory card in the description is assumed to have a part or all of an EPROM (ultraviolet erasable programmable ROM) built-in as a semiconductor storage element. In general, semiconductor memory elements have different structures depending on their type.
There are differences in storage capacity, power supply voltage during writing, write signal pulse width, etc., and there is an extremely wide variety of types. For this reason, a method of providing identification information for each type of semiconductor memory element called an ID code or signature code has recently been widely adopted. Therefore, a structure has been developed in which identification information can be read from a semiconductor memory element having the above-mentioned ID code, and optimal write and read conditions can be automatically set for the semiconductor memory element.

The method for identifying the above ID code will be explained. Third
The figure shows conventional EPROM and EPRO, which are semiconductor memory devices.
It is a connection diagram with M programmer. In the figure, (9 is EPR)
The OM programmer, αQ, is an EPROM.

First, EFROM program 57 (9) Ha, EPROMQ
The address line (usually sV) with the power supply voltage (usually sV) added to Q
2) The input voltages of Ao to A8 and A16--An are set to predetermined voltage values. This voltage value is
The voltage is within the range of oV to the above power supply voltage value.

At the same time, an extremely high voltage (usually 12.5V) is applied to A9 of the address line (2). EPROM
When the QO address input is set, the data line (4
) outputs the ID code set by itself to each terminal of Dx as voltage value information. The EPROM programmer (9) reads this information and
but,.

It is determined what type of semiconductor memory element it is.

Even when using the EPROM programmer (9) as a 27W device for the memory card, the EPROM programmer (9)
) performs a similar operation.

[Problem to be solved by the invention]

Conventional memory card circuits are configured as described above, so there are no countermeasures against the high voltage signals applied from the EPROM programmer, leading to problems such as the risk of the memory card being destroyed. there were.

This invention was made in order to solve the above-mentioned problems.
The purpose is to prevent accidental destruction.

[Means to solve the problem]

The memory card according to the present invention has a constant voltage diode and a resistor inserted in the input circuit.

[Effect]

In this invention, the function of the constant voltage diode is to prevent the application of a voltage higher than the rated voltage value to the input terminal of the semiconductor memory element or the interface semiconductor. do.

FIG. 1 is a circuit diagram of a memory card. In the figure (
1a) to (1n) p (2) to (6) are equivalent to those shown in the conventional example in FIG.
) is a constant voltage diode, and (8) is a resistor. In this example, some or all of the semiconductor memory elements (1a) to (1n) are EPR? This is an example using 5M. Next, the operation will be explained. Third as a 27W memory card device
When using the EPROM programmer (9) shown in the figure,
The EFROM programmer (9) tries to obtain the identification information of the card using the ID code. In operation, one of the address lines (2) A.

A voltage signal of 12.5V is applied from the EPROM programmer (9) to this terminal. This signal is about to be transmitted to the address line (2) AQ inside the memory card. However, the voltage regulator diode provided in this invention (7) (Rated value s
Due to the action of V), a voltage of 5 V or higher is not applied to A9 of the address buffer (5). It is generally known that applying a voltage higher than the power supply voltage to each input terminal of a semiconductor memory element and an interface semiconductor will lead to destruction. Is the rated value of the voltage diode (7) the same as the normally used power supply for the semiconductor elements (1a) to (1n)? [From pressure, 5V
was set. The resistor (8) serves as a current limiting resistor in case the constant pressure diode (7) is short-circuited and destroyed.

〔Effect of the invention〕

As described above, according to the present invention, since a constant voltage diode is provided to protect the input circuit of the memory card, it is possible to prevent electrical damage during writing and reading operations of the memory card.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a memory card according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional memory card, and FIG. 3 is a connection diagram of a conventional EPROM and an EPROM programmer. In the figure, (1a) to (1n) are semiconductor memory elements, (2
) is the address line, (3) is the control line, (4) is the data line,
(5) is an address buffer, (6) is an address decoder, (7) is a constant voltage diode, and (8) is a resistor. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] The input circuit of a memory card incorporating a semiconductor memory element is equipped with a circuit element for the purpose of preventing electrical breakdown of the semiconductor memory element or an interface semiconductor connected to the semiconductor memory element. How to protect memory card input.