JPH07281800A - Peripheral device - Google Patents

Abstract

PURPOSE:To provide the peripheral device which judges whether or not an external peripheral device is connected and the state of power supply to the external peripheral device and controlling the power supply to a card type peripheral device itself according to the judgment result without depending upon the supply of a power source. CONSTITUTION:The card type peripheral device of the PCMCIA, JEIDA standards equipped with a peripheral device control circuit 202, a magnetic disk control circuit 2-3, a semiconductor memory 2-1, and terminating resistors 2-4A and 2-4B is constituted by connecting the collector and emitter of an NPN transistor 2-7 between an insertion/extraction signal terminal 1-1-1 and a ground terminal GND, and connecting the collector and base of this NPN transistor 2-7 to the output terminal of the peripheral device control circuit 2-2 and a newly provided external peripheral device power-ON terminal 2-1-1 through resistors 2-8 and 2-9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a computer peripheral device having a card-type peripheral device connection socket.

[0002]

2. Description of the Related Art Peripheral devices for computers equipped with card-type peripheral device connection sockets have been rapidly becoming popular in recent years, along with the miniaturization of computers. In order to popularize these in the industrial world as well, for example, the Japan Electronic Industry Development Association (hereinafter referred to as JEIDA) and the US P
personal Computer Memory C
ard International Associate
standard (hereinafter referred to as PCMCIA) has established standards.

Initially, these standards were intended to increase the number of semiconductor memories, but later the standards were expanded so that input / output devices such as magnetic disks and modems could be used. It is a standard generally called JEIDA 4.1 or PCMCIA 2.0. Both standards have new extensions, and it seems that various peripheral devices can be connected in the future.

Initially, it was thought that the functions of the portable computer were mainly expanded. However, even in a stationary computer, the peripheral devices that were conventionally incorporated are removed, and a large number of connection circuits for these external peripheral devices are prepared. The models that have done are appearing. This is a computer low power consumption policy Energy StarC promoted by the US Environmental Protection Agency.
In order to meet the standard of the computer programs, the number of peripheral devices that have been always connected so far is reduced, and necessary peripheral devices are connected only when necessary to reduce unnecessary power consumption.

It is considered that such a trend is further advanced, reflecting the recent trend toward energy saving. Therefore, it is considered that there is a movement to downsize the peripheral devices so that they can fit in the size of the card, but it is quite difficult to fit all the peripheral devices in the size of the card. For example, it is physically impossible to fit a secondary storage device that uses an exchange medium having a size standard larger than the size of the card into the size of the card.

In the case of these external peripheral devices, as a coping method which is often found at present, as shown in FIG. 1, a part which does not physically fit in the size of the card type housing 2 is housed in another external housing 4. , A method of performing control via the connection cable 3 is adopted. For example, ANSI X3.131-called SCSI as a connection control standard for magnetic disk devices.
Devices complying with the connection control standard set forth in 1986 are commercially available and widely used, but these devices can be connected to a computer 1 that cannot connect a connection control circuit that is not a card type up to now. A card type housing 2 in which the connection control circuit is housed is commercially available. As described above, the number of external peripheral devices stored in the card type housing 2 or using the card type housing 2 is expected to increase more and more in the future. In order to deal with it, the following new problems have occurred.

First, in the case of an external peripheral device that consumes a relatively large current, since the capacity supplied from the computer main body is limited, the peripheral device must have its own power supply. However, if the peripheral devices are not connected to the power supply and are left connected by mistake, the power supply of the computer itself may be consumed.

First, the first problem will be described with reference to the circuit diagram of the SCSI magnetic disk card shown in FIG. 2 when an external housing containing the magnetic disk 4-1 is connected.

A control signal from the CPUI-7 of the computer 1 is sent from the peripheral device control circuit 2-2 in the card type housing 2 through the card type peripheral device connection circuit 1-4 and the card type peripheral device socket 1-1. Magnetic disk control circuit 2-3
It enters into and is converted into a magnetic disk control signal, enters the external housing 4 through the external peripheral device connection socket 2-1 and the connection cable 3, and is transmitted to the magnetic disk device 4-1.

As shown in FIG. 3, the male terminals (pins) provided in the card-type peripheral device socket 1-1 have an effective corrosion area defined by the standard, and that of the power supply and ground pins is the most. Long, card type peripheral device signal group terminal 1-
1-2 is shorter than that, and the insertion / removal detection signal terminal 1-1-
1 is specified to be shorter.

Therefore, when the card-type housing 2 is inserted into the card-type peripheral device connection socket 1-1, first, the power-related terminals are connected (VCC is still 0V), and then the card-type peripheral device signal group terminal 1-1. -2 is connected (VCC is still 0V), and then the insertion / removal detection signal terminal 1-1-1 is connected (G
ND), and at this time, the card type peripheral device power supply switch 1-5 is turned on, VCC = 5V or 3V, and each signal becomes ENABLE.

Therefore, the card type peripheral device socket 1-1 is provided.
The insertion / extraction detection signal terminal 1-1-1 is in the H logic state by the pull-up resistor 1-6 inside the computer 1 when the card type housing 2 is not inserted,
At this time, the card type peripheral device connection circuit 1-4 shuts off the card type peripheral device power supply switch 1-5 and also shuts off the other card type peripheral device signal group terminals 1-1-2.

On the other hand, when the card type housing 2 is inserted,
Since the insertion / removal detection terminal 1-1-1 is directly connected to the ground side in the card type casing, it is switched to the L logic state, and the card type peripheral device connection circuit 1-4 becomes the card type peripheral device power supply switch 1-5. And the electronic switch (not shown) in the card type peripheral device connection circuit 1-4 is turned on,
The card type peripheral device signal group terminal 1-1-2 is set to the connected state.

According to the PCMCIA and JEIDA standards, the insertion / removal detection signal terminal 1-1-1 is at the TTL level, that is,
The card type housing 2 is supposed to be inserted when the voltage becomes 0.8 V or less.

Further, at both ends of the signal line handling the magnetic disk control signal, that is, at the magnetic disk control circuit 2-3 and the magnetic disk device 4-1, a terminating resistor 2 for preventing waveform deterioration due to a signal transmission path is provided. -4A and 2-4B and 4-2A
And 4-2B are standardized.

This terminating resistor is divided into a ground side A and a power source side B, but the control circuit side and the device side use the same value, and in the standby state both the control circuit and the device are in a non-connection state. Since it becomes (high impedance), in the state where the connection cable 3 is not present, both become the terminal voltage obtained by dividing the power supply voltage by the terminating resistors A and B, and the power is supplied to both the computer side and the external magnetic disk side. In the state where they are in the same state, the potential is the same, so that connecting the connection cable 3 does not consume power on the computer side. However, when the external peripheral device power switch 4-4 on the magnetic disk side is turned off, a large amount of current from the computer side flows into the voltage dividing resistor 4-2A.

As another example, the printer device 5-1
FIG. 4 shows a case where an external peripheral device housed in the external printer device housing 5 is connected via the card type housing 2. Also in this case, the external printer device housing 5 accommodating the conventional printer device 5-1 is connected to the input terminal having the pull-up resistor 5-3 and the TTL signal level generally called the Centronics interface. 1 is a peripheral device control circuit 2-2 of the card-type housing 2
It was designed to be controlled to.

However, also in this case, the printer device 5-1
When the power switch 5-5 of is not turned on,
The power supply signal inside the printer is a pull-up resistor 5-3.
Therefore, the power source 1-2 of the computer 1 is consumed through.

In the above two examples, since the main purpose is to connect the peripheral device which does not fit in the card type casing 2, only the connecting circuit is housed in the card type casing 2, so that the external peripheral device is attached. When the power supply of the side is not turned on, the function of the card-type housing itself is meaningless and rather wastes power.

Next, in order to connect and use a peripheral device of a new type, not limited to the card type casing peripheral device, software (called a device driver) for operating the peripheral device depends on the peripheral device. You will need it. However, at present, computers that can connect card type peripheral devices are limited to small ones mainly for carrying, that is, built-in peripheral devices, and depending on the model, data transfer with other computers is possible. As a means, there are some which can use only card type peripheral devices. Until now, it was common to use floppy disks, but it is not so common for portable computers.

Therefore, in a computer in which only a card type peripheral device can be connected to the outside, in order to use a peripheral device in a new field, in order to supply a device driver,
You will have to use semiconductor memory cards that are much more expensive than floppy disks. Therefore, in order to supply a card-type peripheral device in a new field, if an expensive device driver supply means such as a memory card is not provided separately from the peripheral device, the available computer will be restricted. Will end up. This is the second problem.

Although it is technically possible to provide the card-type peripheral device in a new field with the memory card function, in this case, which of the new peripheral device and the memory card function is to be used? It is necessary to have a means of switching.

The PCMCIA and JEIDA standards allow a peripheral device connection card and a memory card to coexist in the same housing, but the device driver for the memory card installed in a commercially available computer is not a memory. Some reject the handling of cards with mixed functions (it is also defined by the PCMCIA and JEIDA standards that the device driver can ignore the cards that cannot be controlled), and they are mechanically mixed. However, it is possible to connect more computers by providing a means for clearly switching.

It is conceivable that a switch may be provided and the user may switch the switch according to the judgment of the user. However, like the first problem, this cannot positively prevent the user from using the wrong method. Especially in the standards of PCMCIA and JEIDA,
The card in the thinnest case has a thickness of only 3.3 mm, and the small switch that fits in here may not prevent erroneous operation from the viewpoint of visual recognition. This is the third problem.

In order to solve the above-mentioned first to third problems, for example, when the peripheral device is not connected to the outside of the card type peripheral device, that is, when the card type peripheral device is in a form that can be easily visually recognized. Operates as a memory card, operates as a peripheral device connection card when the peripheral device is connected to the outside of the card type peripheral device, that is, when the connection cable is connected, which is also easy to visually recognize, It is only necessary to add a logic circuit that satisfies the logic that the power supply from the computer is shut off or the power supply is not supplied when the power supply to the peripheral device is not supplied. PCMCIA, JEI
According to the DA standard, in order to improve operability, hot plugging / unplugging (connection and disconnection while power is supplied), that is, a card-type peripheral device is plugged in, and power is supplied from the computer for the first time. Therefore, as in the present case, a logic circuit that determines logic before power is supplied cannot be used because a logic circuit IC that can be easily obtained and whose logic can be easily achieved cannot be used. There's a problem. This is the fourth problem.

[00026]

A peripheral device for a computer provided with a card-type peripheral device connecting socket will be developed in the future.
It is expected that the number of devices will continue to increase, but it is obvious that convenience will be greatly impaired unless the software provision of the means of use can be easily provided.

Further, in the utilization means for connecting to a device which does not physically fit in the card type housing, the state where the power of the connected device is not turned on, that is, the state where the device is mechanically connected but cannot be used is simply used. Not only can it not be done, but it must also be avoided because it wastes power.
Moreover, unless these problems are avoided in the state where power is not supplied, it cannot be applied to the excellent use environment of hot plugging and unplugging in the card type peripheral device.

Therefore, according to the present invention, the so-called presence / absence of external (external) peripheral device connection and the power supply state of the external peripheral device are determined, and the power supply control to the card type peripheral device itself is performed based on these determination results. It is an object of the present invention to provide a peripheral device that can perform without relying on the power supply.

[0029]

As described above, the PCMC
According to the IA and JEIDA standards, the insertion / removal detection signal terminal 1-1
When -1 becomes the TTL level, that is, 0.8 V or less, it is considered that the card-type housing is inserted. Therefore,
If it can be set to 0.7V, the card will be inserted and a voltage of 0.7V can be obtained.
Therefore, in order to make the card-type housing effective when the external peripheral device is not connected, it can be realized by using an element that is turned on by applying a positive voltage of less than 0.8V. Also, when the external peripheral device is connected and the card-type housing is enabled when the power supply of the external peripheral device is being supplied, the switching element is controlled by the external power supply (however, positive voltage) itself. This will solve the problem.

The present invention is based on this technical idea, and in a PCMCIA or JEIDA standard card type peripheral device, a switching element is inserted between the conventional card type housing and the insertion / extraction detection signal terminal directly connected to the ground signal terminal. And the voltage of the insertion / removal detection signal pulled up by the power supply on the computer side and the power supply voltage of the external peripheral device,
By turning on and off the switching element, the insertion / removal detection signal is controlled.

[0031]

According to this method, the insertion / removal detection signal terminal 1-1-
When 1 is connected to the ground signal terminal via the switching element inside the card type casing, power is supplied from the computer even if an external peripheral device is connected unless the switching element is in a conductive state. Because there is no such thing
Prevent wasting power. A function to connect the semiconductor memory to the computer when the semiconductor memory is built in the card type peripheral device or to connect the external peripheral device to the computer, and to shut off the semiconductor memory from the computer when the external peripheral device is connected. Can have

[0032]

FIG. 5 shows an embodiment of the present invention in which the problems of the prior art shown in FIG. 2 are improved. The difference from the embodiment shown in FIG. 2 is that the card type housing 2 is different. , A semiconductor memory 2-11 is provided in parallel with the magnetic disk control circuit 2-3, and the insertion / extraction detection signal terminal 1-1-1 and the ground terminal G are provided.
The collector and the emitter of the NPN transistor 2-7 used as a switching element are connected between ND, and the collector and the base of the NPN transistor 2-7 are the resistors 2 respectively.
External peripheral device power-on detection terminal 2 newly provided together with the output terminal of the peripheral device control circuit 2-2 via -8 and 2-9.
It is a point connected to 1-1.

The external case 4 is different in that an external device equivalent resistor 4-5 is connected between the external peripheral device power-on detection terminal 2-1-1 and the ground terminal GND.

Therefore, when the external peripheral device 4 is not connected,
Since the external peripheral device connection connector 2-1 is open, the base of the NPN transistor 2-7 is the resistor 2-8.
When the series combined value of the resistor 2-8 and the resistor 2-9 connected to the collector through the resistor 2-9 is sufficiently small, a voltage is applied to the collector of the NPN transistor 2-7 (card type). When the peripheral device housing 2 is inserted into the socket 1-1), the collector voltage base voltage (hereinafter VBE)
And ) Is almost equal to
It will be about 0.6V. Collector current at this time (hereinafter IC
Is the current that biases the pull-up resistor 1-6 and the card-type peripheral device connection circuit 1-4, the maximum value is clarified by the standard.

Therefore, in order to allow the current value to flow and the collector terminal voltage to be less than 0.8 V, the value of the resistor 2-8 is R28, the value of the resistor 2-9 is R29, and the transistor 2 is used.
If the DC voltage gain of -7 is hFE,

R28 + R29 <(0.8−VBE) ÷ (IC ÷ hFE) (Equation 1)

It suffices to satisfy the relationship of

Next, when the external housing 4 is connected, the power switch 4-4 is turned on and the power 4-3 is supplied, the external peripheral device power supply terminal 2- of the external peripheral device connection socket 2-1.
From 1-1, the power supply 4-3 of the external peripheral device is applied to the base of the NPN transistor 27 through the resistor 2-8,
The NPN transistor 2-7 becomes conductive.

If IBE is the maximum current value that can flow in the base of the NPN transistor 2-7 and VDD is the power supply voltage of the external peripheral device,

R28> (VDD-VBE) ÷ IBE (2 expressions)

The NPN transistor 2-7 is not destroyed as long as the above relation is satisfied.

Also, although external peripheral devices are connected,
When the power supply 4-3 is not supplied, the external peripheral device power supply terminal 2-1-1 pulls the value of the equivalent resistor 4-5 in the power supply state of the external peripheral device to R45 and pulls the internal computer 1. When the value of the up resistor 1-6 is R16 and the power supply voltage of the computer 1 is VCC, the NPN transistor 2-7
To turn off, that is, the base voltage is less than VBE

VBE> VCC × R45 ÷ (R16 + R29 + R45) (Formula 3)

It is necessary to satisfy the relationship By the way, since the insertion / removal detection signal terminal 1-1-1 is regulated to have a value equal to or more than half the value of VCC for the H level, it is necessary to satisfy this condition as well.

It is necessary to satisfy the condition of 1 ÷ 2 <R16 ÷ (R16 + R29 + R45) (Equation 4) together. Strictly speaking, it is necessary to consider the current flowing into the card type peripheral device connection circuit 1-4 in this equation, but in that case, the resistor 1-
6 has a resistance in parallel, that is, the value of R16 is small, so if R29 and R45 satisfying equation 4, R1
Even if the value of 6 becomes small, there is no problem because the magnitude relation of the inequality of the above Expression 4 is satisfied as it is.

The external device power supply terminal 2-1-1 is also
It is obvious that the signal can be used as it is as a signal for switching whether to use it as a memory card for supplying a device driver or to use it as an external peripheral device card. In this embodiment as well, the peripheral device control circuit 2 can be used as it is.
-2 to switch which of the semiconductor memory 2-11 and the timing disk control circuit 2-3 is connected to the computer 1 side.

In the embodiment, the problem is solved by setting the constants satisfying the above expressions 1 to 4 and switching the object connected to the computer 1 by turning on / off the external power supply.

FIG. 6 shows another embodiment. This embodiment is an embodiment of the present invention which improves the problem of the conventional card type peripheral device shown in FIG. 4, but in addition, another method is used for the circuit for detecting the connection state of the external peripheral device. It was what I had.

In this embodiment, since the collector voltage of the NPN transistor 2-7 becomes less than 0.8V when the external peripheral device is not connected,

R29 <(0.8-VBE) ÷ (IC ÷ hFE) (Equation 5) may be satisfied.

When external peripheral devices are connected and power is supplied,

R28> (VDD-VBE) ÷ IBE (Equation 6)

It suffices if

Although external peripheral devices are connected,
When the power is not supplied, assuming that the value of the equivalent resistor 5-6 in the unpowered state of the external peripheral device is R56 and the apparent voltage of the diode 2-10 is VF,

VBE> (VCC-VF) × R56 ÷ (R16 + R29 + R45 + VF (Equation 7)

And

VCC / 2 <(VCC-VF) × (R29 + R56) ÷ (R16 + R29 + R56) + VF (Equation 8)

It suffices if

Of course, also in this embodiment, the external device power supply terminal 2-1-1 is used to switch whether to use it as a memory card for supplying a device driver or the like, or as an external peripheral device card. Equation 5 above
The problem was solved by setting a constant to a value satisfying ~ 8.

FIG. 7 shows another embodiment. This embodiment is an improvement over the problems of the conventional card type peripheral device shown in FIG. 2, but some of the functions of the present invention. Is assigned to the external peripheral device side.

In this embodiment, a switch 2-13 is provided in the card-type housing 2 and an NP is provided in the external housing 4.
Adjacent to the one provided with the N-transistor 4-6 and the resistors 4-7 and 4-8, it is turned off when the external peripheral device connection cable 3 is inserted and turned on when it is unplugged. ing.

Therefore, when the card type housing is inserted by itself, the insertion / removal detection signal terminal 1-1-1 is conducted to the ground terminal side, so that the insertion is detected. On the other hand, when the external peripheral device connection cable 3 is plugged in, the switch 2-13 is in the off state.
Through 3, the insertion / removal detection signal terminal 1-1-1 does not become conductive with the ground terminal side.

In this embodiment, an NPN transistor 4-6 is provided on the external peripheral device side, and the collector is connected to the external peripheral device connection cable 3 and the external peripheral device connection detection terminal 2.
-1-3, is connected to the insertion / extraction detection signal terminal 1-1-1, and the base terminal of the NPN transistor 4-6 is the resistor 4
Since it is connected to the external device power supply 4-3 via -7, when the external device power supply 4-3 is on, the collector and emitter of the NPN transistor 4-6 become conductive, and the card-type housing 2 becomes , Card peripheral device connection socket 1-1
When it is plugged in, the insertion / removal detection signal terminal 1-1-1 is grounded to be in a conductive state, and it is detected that it is plugged in.

Needless to say, the same effect can be obtained even if the NPN transistor 4-6 is replaced with a normally-off type mechanical relay.

In this embodiment, since it is not possible to judge from the external peripheral device detection terminal 2-1-3 whether or not the external device is connected, the external peripheral device connection detection terminal 2-1 is newly added.
The signal from -3 is used. This terminal is open in the card type housing, and pull-up resistor 2
Although it is at a high level by -12, when the external magnetic disk device housing 4 is connected, it becomes a grounded state, that is, a low level. Therefore, the card operation state is switched by this signal. The above has solved the problem.

(Different Embodiment) The embodiment shown in FIG.
External peripheral device connection cable 3 pulled out from the external housing 4
External peripheral device connection socket 2 in which the card type housing 2 is provided
-1, but when the external peripheral device connection cable 3 is pulled out from the guard type casing 2 and the socket is provided on the external casing 4 side, the switch 2-1 is connected.
3 is provided in the outer housing 4.

[0067]

As described above, according to the present invention, a peripheral device which does not fit in the card type housing is connected via the card type peripheral device housing 2. In the card type peripheral device alone, a device driver is used. It can be used as a memory card that supplies power, and when the peripheral device is connected to the outside of the card type peripheral device, the function is switched as a peripheral device card and power is supplied to the externally connected peripheral device. If there is no card, the insertion / removal detection function of the card-type peripheral device itself is disabled and the computer 1
This has the effect of cutting off the power supply from the power source and preventing the power from being wasted due to misuse, and the effect that the number of additional parts for that purpose is extremely small.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of connecting a peripheral device, which does not fit in a conventional card-type housing, using a card socket.

FIG. 2 is a circuit diagram showing a connection state of a magnetic disk device connection card for using a magnetic disk device that does not fit in a card type housing.

FIG. 3 is a view showing an effective contact area of each male terminal provided in a card-type peripheral device socket.

FIG. 4 is a circuit diagram showing a connection state of a printer device connection card for using a printer device that does not fit in the card housing.

FIG. 5 is a circuit diagram showing a connection state of a magnetic disk device card to which the present invention is applied and which uses a magnetic disk device that does not fit in a card housing.

FIG. 6 is a circuit diagram showing a connection state of a printer device connection card for using a printer device to which the present invention is applied and which does not fit in a card housing.

FIG. 7 is a circuit diagram showing a connection state of a card for connecting a magnetic disk device to which the present invention is applied and which does not fit in a card housing.

[Explanation of symbols]

 1 Computer 1-1 Card Type Peripheral Device Connection Socket 1-1-1 Insertion / Extraction Detection Signal Terminal 1-1-2 Card Type Peripheral Device Signal Group Terminal 1-2 Computer Power Supply 1-3 Computer Power Switch 1-4 Card Type peripheral device connection circuit 1-5 Card type peripheral device power supply switch 1-6 Pull-up resistor 1-7 CPU 2 Card type housing 2-1 External peripheral device connection socket 2-1-1 External peripheral device power supply terminal 2- 1-2 External peripheral device power-on detection terminal 2-1-3 External peripheral device connection detection terminal 2-2 Peripheral device control circuit 2-3 Magnetic disk control circuit 2-4A-B Termination resistor 2-5 Printer connection circuit 2-6 Printer connection buffer circuit 2-7 NPN transistor 2-8-9 resistor 2-10 diode 2-11 semiconductor memory 2-12 pull-up Resistor 2-13 Switch 3 External peripheral device connection cable 4 External housing 4-1 Magnetic disk 4-2A-B Terminating resistor 4-3 External peripheral device power supply 4-4 External peripheral device power switch 4-5 External peripheral device Equivalent resistor 4-6 NPN transistor 4-7-8 Resistor 5 External printer device housing 5-1 Printer device 5-2 Input buffer 5-3 Pull-up resistor 5-4 External printer device power switch 5-5 External printer Device equivalent resistor 5-6 External peripheral device equivalent resistor

Claims (4)

[Claims] 1. PCMCIA, JE for use by connecting to a computer equipped with a card-type peripheral device connection socket
In the IDA standard card type peripheral device, a switching element is provided between the insertion / removal detection signal terminal and the ground signal terminal, and the voltage of the insertion / removal detection signal pulled up by the power supply on the computer side and the voltage via the card type peripheral device. A control circuit for turning on / off the switching element according to the power supply voltage of the external peripheral device connected to the computer is provided, and when the power supply for the external peripheral device is not supplied, the control circuit turns off the switching element. As a peripheral device, the connection detection circuit on the computer side is disabled to prevent power consumption on the computer side. 2. In a PCMCIA or JEIDA standard card type peripheral device equipped with a semiconductor memory which is used by connecting to a computer equipped with a card type peripheral device connection socket, a switching element is provided between an insertion / removal detection signal terminal and a ground signal terminal. The switching element is turned on and off by the voltage of the insertion / removal detection signal provided and pulled up by the power supply on the computer side and the power supply voltage of the external peripheral device connected to the computer through the card type peripheral device. At the same time, when the external peripheral device is not connected, the switching element is turned on to connect the semiconductor memory to the computer, and when the external peripheral device is connected, the switching element is turned off to shut off the semiconductor memory from the computer. A peripheral device having a control circuit for controlling. 3. The peripheral device according to claim 1, wherein an NPN transistor is used as a switching element, and the control circuit is composed of a proper number of resistors or a proper number of resistors and diodes. 4. A switch which is turned off when an external peripheral device connection cable is connected as a switching element, and an NPN.
A transistor is used, the switch is provided in a card-type peripheral device or an external peripheral device, and a control circuit using an appropriate number of resistors and the NPN transistor are provided in the external peripheral device. Peripheral device according to any one of 3.