HK1009685B - Coupler for managing communication between a portable data medium and a data exchange device, and data exchange device therefor - Google Patents

Description

Coupler for managing communication between a portable data recording medium and a data exchange device and data exchange device for use therewith

The invention relates to a coupler for managing communication between a portable data recording medium and a data exchange device. At the data switching device side, the communication uses at least one data transmission signal and two control signals, the signals being transmitted by the data switching device in one of a predetermined first and second input sequence. At the data recording medium side, the communication uses at least a data recording medium power signal, a data recording medium reset signal, and a data transfer signal.

The coupler may be used, for example, to restrict access to a computer network to authorized persons who have portable data recording media for this purpose, such as a chip card (chip card) equipped with a microprocessor or micro-wired logic circuit, which defines an area to which access is controlled so that confidential information such as a cryptogram can be maintained (see, for example, the portable object described in U.S. patent No. 4211919).

The protocol for exchanging with chip cards is compiled according to international standard I807816-3, which specifies the sequence of generating signals suitable for chip cards, namely a power supply signal VCC, a memory power supply signal VPP, a reset signal RST, a clock signal CLK and a data exchange signal I/O. The standard specifies explicitly the order in which these signals appear and disappear.

A coupler of this type can comprise, in a well-known manner, a microprocessor which controls its interface with the portable data recording medium and is controlled by a data exchange device which constitutes a central processor. The microprocessor slows down the exchange process between the asynchronous data exchange device and the portable data recording medium.

In order to avoid the use of microprocessors in the coupler, it is proposed that signals are provided by a serial port of the data exchange device, in particular a port based on the RS232 standard, namely a "clear to send" signal CTS, a request to send signal RTS, a "data carrier detect" signal DCD, a "data terminal ready" signal DTR, a data transmission signal TX and a data reception signal RX, for generating signals suitable for portable data recording media.

This type of coupler is described in us patent 5149945. The order of the signals supplied to the chip card is exclusively defined by the data exchange device, and the coupler cannot interfere with this order, thus allowing special operating conditions at one end of the chip card.

One consequence is that the above criteria cannot always be met, in particular when the chip card is reinserted after being removed during communication with the data exchange device, since the chip card is rapidly re-powered, the data exchange device is not given enough time to recover to join a re-power according to a standardized sequence.

Thus, it appears to be desirable to enable the coupler to interfere with the order of signals transmitted by the data exchange device in order to provide a greater range of control and test modes of the chip card.

The object of the present invention is to eliminate the above-mentioned disadvantages, for which purpose it relates to a coupler as described at the beginning of the application, characterized in that:

-it comprises bistable control means which are input activated by at least two control signals transmitted by the data exchange device and are designed to output at least a power supply signal and a reset signal of the data recording medium within one of a predetermined first and second two output sequences, which is a function of the input sequence;

the first input sequence alone is capable of generating a first output sequence comprising in turn the power signal and the reset signal of the data recording medium, which allows the data exchange device to enter into communication with the portable data recording medium.

In this way, the bistable control means make it possible to intervene in the sequence of signals transmitted by the data exchange device, in order to generate from these signals and as a function thereof signals that arrive directly at the chip card, as will be more clearly described in the attached figures. The bistable control device makes it possible to control the chip card, this control simultaneously serving as a function of the instantaneous action of the data exchange device and as a function of the instantaneous action of the chip card.

The invention also relates to a data exchange device designed to manage communication with a portable data recording medium. The device comprises data exchange means and coupling means for this purpose, such as the coupler defined above. Wherein the coupling means further comprises means for detecting the presence of the portable data recording medium, arranged to send a medium presence signal to the data exchange means upon receipt of the first control signal when the portable data recording medium and the coupling means are matched; wherein the data exchange means are designed to periodically send the second input sequence to the coupling means before communicating with the portable data recording medium until they receive a signal that the portable data recording medium is present.

Further characteristics and advantages of the invention will appear from the following description, given by way of illustrative and non-limiting example, with reference to the accompanying drawings, in which:

FIG. 1 shows a structure incorporating a coupler according to the present invention;

FIG. 2 is a block diagram of a coupler;

FIG. 3 illustrates a protocol exchanged with a chip card according to the ISO7816-3 standard;

fig. 4 shows the sequence of signals provided by the data switching device;

FIG. 5 is a partial view of the coupler in relation to the internal power supply;

FIG. 6 is a partial diagram of a coupler associated with generating a signal suitable for use with a portable data recording medium; and

fig. 7 is a partial diagram of a coupler associated with transmitting a data signal.

Fig. 1 shows the structure of a typical personal computer 1 in which there is a port connector 2, for example a serial port of the RS232 type, which is connected by a cable 3 to a serial port connector 4 of a coupler 5. The coupler 5 further comprises a connector 6 capable of receiving a chip card of the chip card 7. The interface device 5 is intended to manage the data exchange between the chip card 7 and the personal computer 1; in particular, the coupler 5 can be used to implement security functions, such as providing a chip-based identification card to authorized persons for controlling access to a computer or computer network.

Fig. 2 is a block diagram of a coupler 5, the coupler 5 receiving signals RTS, DTR, CTS, TX, RX and DCD from the serial connection line of the computer 1 through a serial port connector 4; its chip card connector 6 comprises plugs for connecting VCC, RST, CLK and I/O signals of the chip card and a plug for connecting a card presence switch (card presence switch)31, which card presence switch 31 is closed by the chip card when the chip card is inserted into the connector 6.

The DTR signal is fed via a chip card switch 31 together with the signal RTS into a bistable circuit 25 which controls a power supply circuit 12 and a blocking circuit 23. The role of the bistable circuit 25 is that of authorization, first of all, the supply of the supply voltage VCC directly to the coupler circuit, in particular to the circuits 29, 32, 41 and to the chip card 7; second, transmission of the signal RST through the blocking circuit 23. The grant is only transmitted when the DTR and RTS signals are activated in the order DTR, RTS.

The card presence switch 31 is connected to the signal CTS in order to return the chip card presence information to the serial port connector 4.

The VCC signal is sent to the interface circuit 29 which generates the RST signal, the clock signal generator which generates the CLK signal, and the interface circuit 41 which generates the I/O signal, since the signals RST, CLK and I/O are generated by the signal VCC, which ensures that their voltages are lower than the signal VCC and meets the requirements of the ISO7816-3 standard.

The coupler 5 further comprises a power supply 11 which drives a power supply circuit 12 to supply the stable signal VCC, and a comparison circuit 14 which compares the level of the power supply 11 with a reference level, which in this case is constituted by the stable signal VCC.

Comparator circuit 14 outputs a so-called "low" level of the power supply and transmits it to signal DCD via interface circuit 41.

The reference potential signal GND is transmitted from the computer directly to the chip card via the coupler 5.

In general, the data exchange with chip cards IS compiled according to the IS07816 standard, whose sections 7816-3 relate to the sequence of the different signals applicable to the chip card, i.e. the reference potential signal GND, the power supply signal VCC, the memory power supply signal VPP, the clock signal CLK, the reset signal RST and the data exchange signal I/O, as shown in the timing diagram of fig. 3.

It can be seen that during the set-up handover, the signals VCC, VPP, CLK and RST must be provided in this order; the signal VPP, which is not normally used, is short-circuited by the connection signal VCC. At the end of the exchange, the signals must disappear in the reverse order.

FIG. 4 is a timing diagram of signals sent from the serial connection line of the computer to the coupler 5; it distinguishes three different operation types, corresponding to the following three cases:

the computer reads (i.e. tests) the presence of the chip card without supplying power to the chip card, without the aid of the voltage source 11;

normal access to the chip card when the chip card is supplied with energy, with the aim of the computer to talk to the chip card;

-removing the chip card during normal access.

The first line in fig. 4 defines the position of the chip card relative to the coupler. It comprises a high state (high state) corresponding to the insertion of the chip card into the coupler to the point where not only the chip card and the coupler are electrically connected but also the turning off of the card presence switch 31; also included is a low state (lowstate), which corresponds to the absence of a chip card. The following lines DTS and RST (bistable control circuit 25), CTS (chip card present state), VCC (card power supply) and RST (card reset) all have two states, a high state and a low state, the first of which corresponds to an activation signal. Finally, the last line DCD (Battery deficient status) has alternating shaded and bright areas, the latter including a "valid" annotation indicating the status of the battery that can be tested.

In a first type of operation, it can be seen in particular that the computer sends a signal RTS before a signal DTR, this sequence being periodically generated until the card is detected, detecting the transmission causing the signal DTR to a signal CTS indicating the presence of the card, but not activating the signal VCC, since it is assumed that in this case the order DTR-then-RTS is not followed: therefore, neither signal RST nor signal DCD is activated. During partial removal of the chip card when the three signals RTS, DTR and CTS are activated, only the latter CTS is deactivated. To generate a new DTR, RTS sequence, the computer first changes these signals to a low state in reverse order.

In order to coincide with the inherent operating time of bistable circuit 25, the time interval TDR separating signals RTS and DTR (when signal RTS has been established before signal DTR is activated) is at least equal to the delay of the logic gate, i.e. of the order of a few microseconds. The time interval TRDI separating the withdrawal of the signal RTS from the withdrawal of the DTR is of the same order of magnitude.

Preferably, the first type of operation is triggered periodically in order to detect the insertion of the chip card into the coupler before power-up. Also, it is preferable to periodically confirm the presence of the chip card during an established communication (in particular to ensure that the user of the coupler is indeed authorized and that the chip card is not surreptitiously replaced by a non-legitimate chip card), the operation of the first type being retriggered as many times as desired.

In the second type of operation, the computer sends a DTR signal before the RTS signal as required by the ISO7816-3 standard. Unlike the previous type, when the chip card is fully inserted, the activation of the signal DTR results not only in the activation of the CTS signal, but also in the activation of the VCC signal, which the chip card uses to respond to the computer; activation of the signal RTS causes activation of the chip card reset signal RST which triggers the active operation of the chip card. It must be noted that activation of the VCC signal causes the CLK signal, not visible in fig. 4, to be activated before activation of the RST signal.

At the end of the computer's communication with the chip card, the computer first returns the RTS signal to a low state, which causes the RST signal to be deasserted, and then the computer returns the DTR signal to a low state, which causes the CLK signal, not visible in fig. 4, to be deasserted, followed by the VCC signal being lowered in voltage. Referring to fig. 2, as explained above, in fact, the voltages of the RST and CLK signals are derived from the voltage of the VCC signal, thus ensuring the ordering.

It is to be noted that the order of the signals DTR, RTS defined by the computer is linked to the coupler definition, which makes it possible to meet the requirements of the ISO7816-3 standard indicated in fig. 3 with regard to powering up and down of the chip card. Also to comply with this standard, the duration TRD3 coincides with the minimum time that the RST is activated by the RTS upon power up by the DTR; and the duration TBV coincides with the wait time after the coupler is powered up before reading the battery status.

Referring to fig. 5, if the power supply voltage VBB defined below falls below the reference voltage, a "battery short" state is transmitted to the signal DCD. The following is the action seen from the computer:

if the chip card is powered up (DTR active) and the battery is good, the DCD signal is high (at-12V).

If the "battery short" signal occurs, DTR is active, the DCC signal takes a low value (at +12V) and has a pause (time-out) TBV relative to the VCC signal.

The detection of the battery shortage may be performed until the end of the communication.

It is noted that the above-mentioned second type of operation can be performed after a valid detection of the presence of the chip card followed by the first type of operation, or can also be triggered directly.

In a third type of operation, when the computer-chip card dialog has been established according to the second type of operation described above, the chip card is removed, so that the RST signal is deactivated, the CLK signal, which is not visible in fig. 4, is deactivated, and subsequently the VCC signal voltage is lowered. Even such undo may occur in a shorter period of time associated with the second type of operation. When the chip card is removed, the battery status signal DCD is also deactivated.

Advantageously, the effect of reinserting the chip card is to reactivate the CTS signal, not the VCC, CLK and RST signals. This prevents the disadvantage of the known card presence switch 31 due to the influence of the rebounding of the switch 31, wherein the card presence switch 31 randomly activates the power supply signals VCC and CLK, RST.

In this case, as in the first class of operation, the computer causes the DTR signal and then the RTS signal to be deasserted, followed by the TRD2 with the same time delay as the TRD 1. The cancellation of the signal DTR results in the CTS signal, which is also in a high state, being cancelled.

Fig. 5 is a first partial view of a coupler according to the present invention and involving the coupler power supply. Referring to fig. 2 the coupler comprises a power source 11, which in this case is integrated and constructed from a voltage source, which comprises for example an electric generator, such as a combination of two batteries, a photovoltaic cell or a high-capacity capacitor. The voltage VBB of this voltage source 11 is transmitted via the positive terminal of VBB to a supply circuit 12 of a known kind and providing a standard voltage VCC of 5V, which is used in the coupler 5 and is also suitable for the chip card 7. The power supply circuit 12 is controlled by a signal applied at 13.

The voltage VBB is also transmitted to a "low battery" detection circuit comprising a comparison circuit 14 of fig. 2 which compares the voltage VBB with a threshold value obtained from the voltage VCC and provides a "low battery" warning signal via an output 15.

An external power supply may also be provided, delivered by the socket 16 and regulated by a regulator 17, the output of the regulator 17 being connected to the positive terminal of the voltage source 11 and to the regulator 12.

An external power source may be used to charge the voltage source 11 when the voltage source 11 is rechargeable (battery or bulk capacitor).

Fig. 6 is another partial diagram of a coupler according to the invention, which relates to the generation of a signal suitable for a chip card 7, and the detection of the presence of the chip card.

The signal RTS drives a first input of nand gate 21 through inverter 22; which is connected to a first input of a further nand-gate 23 via a further inverter 33 constituting the blocking circuit of figure 2. The signal DTR passes through two series-connected inverters 24, driving a second input of the gate 21 and a first input of an RS-type flip-flop 25, consisting of two nand gates, in accordance with the bistable circuit of fig. 2, a second input of the flip-flop 25 being received from the output signal of the gate 21. A first output of flip-flop 25 provides a power control signal at 13, which is in accordance with power supply circuit 12 at terminal 13.

A second output of flip-flop 25 is transmitted to a second input of gate 23, the output of gate 23 controlling an NPN transistor 28 connected between supply voltage VCC and ground through an inverter 27, the collector of the transistor providing signal RST through an inverter 29 constituting the interface circuit of fig. 2. All gates in the circuit of the figure, which are arranged upstream of the transistor 28, are energized by the voltage VBB of the voltage source 11 in such a way that the circuit is always on standby, and are able to generate a signal when there is no supply signal VCC.

One input socket of the port connector 2, which transmits the signal DTR, is connected to another socket of the same connector, the connector 2 receiving the signal CTS through a card presence switch 31, the card presence switch 31 being associated with the chip card connector 6 and being closed when the chip card 7 is in the position of the connector 6.

Also, a quartz oscillator 32, which constitutes the clock generator of fig. 2 and is activated by the supply signal VCC, provides a clock signal CLK, whose delay coincides with the logic gate delay.

It can be seen that the logic gate of fig. 6 makes it possible to obey the order of the signals VCC, CLK and RST. As a result, the signal DTR is first used, which is controlled by software installed in the personal computer, due to the fact that it is the process of normal access, the flip-flop 25 first providing the power control signal 13 activating the stabilizing circuit 12. The stabilizing circuit 12 then provides the signal VCC. Next, when the RTS signal is present, the flip-flop 25 changes state and activates the generation of the signal RST, which is present only when the VCC signal is established.

The clock signal CLK can only be generated when the supply signal VCC is established because the crystal oscillator 32 is controlled by the supply signal VCC.

During a read cycle in which the card is present (see fig. 4), the signals DTR and RTS are used in reverse order and the flip-flops do not activate the generation of the signals VCC, CLK and RST, in particular the voltage source 11 remains in the wait state. The presence of the chip card closes the card presence switch 31, which sends the information of the card presence to the computer by means of the signal CTS; since the power supply circuit 12 is not activated, the card presence detection operation occurs without resorting to a voltage source.

The chip card presence information provided by the signal CTS enables the real-time management of the presence of the chip card by means of the personal computer; this makes it possible in particular to detect the removal of the chip card during the exchange of data in order to carry out a session of inactive (task-ended) activity.

Fig. 7 is another partial view of a coupler, the main function of which is to transmit data signals between a computer and a chip card. The interface circuit 41 of fig. 2 performs the conversion of the signals TX, RX and DCD it receives or generates. Here, an NPN transistor 42 is provided, the collector of which is connected to the voltage VCC via two series resistors 45, 46 and the emitter of which is connected to ground. The base of the transistor 42 is driven by a signal TX generated from the interface circuit 41 when its collector is connected to the I/O terminal of the chip card connector. The collector is connected to an inverter of the interface circuit 41 that outputs the RX signal.

The output 15 of the comparison circuit 14 of fig. 5 drives an inverter 44 of an inverter whose output is connected to the interface circuit 41, the interface circuit 41 outputting the "out of battery" warning signal DCD.

Interface circuit 41 and inverter 44 are powered by voltage VCC.

The control signal 13 of the power supply circuit 12 of fig. 5 controls a mosfet 43 directly polarized by a positive voltage, which accelerates the fall of the power supply signal VCC upon power down, thereby causing CLK, RST and I/O to fall, so as to obtain a fall time from 5V to 0.4V shorter than the contact slip time of the card, thereby complying with the ISO7816-3 standard which indicates that the voltage should be lower than 0.4V when the contact is broken.

In operation, the interface circuit 41 ensures multiplexing/demultiplexing between the signals TX, RX side and I/O side. It is noted that the "low battery" signal DCD more generally constitutes a warning signal which is able to detect other abnormal conditions, such as a contact short caused by an unqualified chip card.

The use of an integrated voltage source enables a completely secure use of the signal for the chip card without the need to obtain power from a personal computer, which is important in the case of a portable computer.

Also, the coupler according to the present invention has a simple design, which enables low price and reduced volume; in this way, an interface device corresponding to the size of a chip card can be produced.

In the above example, the specific signals RTS, DTR, CTS and DCD derived from the serial connection line of the data exchange device are selected to cooperate with the coupler, and each of them is assigned a specific function by the operation of the portable data recording medium. It is to be understood that the invention is not limited to this particular choice. More generally, any signal derived from the data exchange device via the serial connection line that conforms to the communication protocol of the connection line may take the role of any RTS, DTR or DCD signal; similarly, any signal returned to the data exchange device via the serial connection line that conforms to the communication protocol of the connection line may play the role of signal CTS (e.g., in an RS232 connection line, data-set-ready signal DSR).

Furthermore, when the above-mentioned coupler is designed for carrying out a serial data signal transmission, it will be clear that the invention is also applicable to the transmission of parallel data signals, in which case the data exchange device and the portable data recording medium comprise suitable interface means.

The above-mentioned coupler is described as a device physically separate from the data exchange device and the portable data recording medium, but it can of course be integrated into either of these devices on the other hand. In this case, the connection means between the device and the coupler referred to in the question, for example the connector or the cable referred to in fig. 1, can be deleted.

Also, in the second and third classes of operation of fig. 4, the CTS signal is not used, in accordance with a less preferred embodiment. In fact, powering up of the chip card in the second type of operation and powering down of the chip card in the third type of operation do not require management of the signals in order to comply with the ISO7816-3 standard.

Claims (8)

1. A coupler for managing communication between the portable data recording medium (7) and the data exchange device (1), at one end of the data exchange device, the communication using at least one data transmission signal and two control signals, which are transmitted by the data exchange device in one of a predetermined first and second input sequence; at the data recording medium side, the communication using at least a data recording medium power supply signal, a data recording medium reset signal, and a data transfer signal, which signals are generated by the signal generating means (29, 32, 41) of the coupler, characterized in that:

-it comprises bistable control means (25) which are input-activated by at least said two control signals transmitted by the data exchange device and are designed to activate said means for generating signals so that they output at least a power supply signal for said data recording medium and a reset signal for said data recording medium in one of a predetermined first and second output sequence, which is a function of said input sequence;

-said first input sequence alone being capable of generating a first output sequence comprising in turn a power supply signal for said data recording medium and a reset signal for said data recording medium, which allows the data exchange device to enter into communication with the portable data recording medium.

2. A coupler according to claim 1, characterized in that it comprises means (31) for detecting the presence of a portable data recording medium, designed to send a medium presence signal to the data exchange means upon receipt of a first of said control signals when the portable data recording medium and the coupling means are matched, said second input sequence sent by the data exchange device allowing it to detect the presence of the portable data recording medium while the latter is not supplied with power.

3. A coupler according to claim 1, in which the means for generating the signal (29, 32) are designed to:

-receiving said power supply signal having a predetermined level; and

-transmitting said reset signal and a clock signal from said power supply signal to the portable data recording medium in such a way that their levels are lower than a predetermined level of said power supply signal.

4. A coupler according to claim 3, wherein said signal generating means (29, 32, 41) is designed to receive said data transmission signal transmitted by the data exchange device; and for transferring said data transmission signal from said power supply signal to a portable data recording medium at a level lower than a predetermined level of said power supply signal.

5. A coupler according to claim 1, characterized in that:

-the portable data recording medium cooperates with the coupler by means of respective sliding contact means (6); and

-said means for generating signals comprise attenuating means (43) for the power supply signal, designed to attenuate the level of the power supply signal during communication until a predetermined threshold level is reached, before said respective sliding contact means stop cooperating with each other.

6. A coupler according to claim 1, wherein:

-said means for generating a signal comprise a power source (11, 12, 23, 29).

7. A data exchange device designed to manage communication with a portable data recording medium (7), comprising for this purpose data exchange means (1) and coupling means (5), at one end of which the communication uses at least one data transmission signal and two control signals, the signals being transmitted by the data exchange means (1) in one of a predetermined first and second input sequence; at the data recording medium side, the communication uses at least a data recording medium power supply signal, a data recording medium reset signal, and a data transfer signal, which are generated by signal generating means (29, 32, 41) of the coupler, characterized in that the coupling means (5):

-comprising bistable control means (25) input-activated by at least one of said two control signals transmitted by the data exchange means (1) and designed to activate said means for generating signals so that they output at least a power supply signal for said data recording medium and a reset signal for said data recording medium in one of two predetermined first and second output sequences, which is a function of said input sequence;

-being designed such that said first input sequence alone is capable of generating a first output sequence comprising in turn a power supply signal for said data recording medium and a reset signal for said data recording medium, which allows the data exchange device (1) to enter into communication with the portable data recording medium;

-comprising means (31) for detecting the presence of a portable data recording medium, designed to send a medium presence signal to the data exchange means (1) upon receipt of a first control signal when the portable data recording medium and the coupling means (5) are matched, said second input sequence sent by the data exchange means (1) allowing it to detect the presence of a portable data recording medium while the latter is not supplied with power,

the data exchange means (1) are designed to periodically send said second input signals to the coupling means (5) before communicating with the portable data recording medium until they receive a signal that said portable data recording medium is present.

8. A data exchange device according to claim 7, wherein the data exchange means (1) is arranged to transmit said first input sequence upon detection of the presence of the portable data recording medium.