Method and apparatus for communicating with a host

• US 6,543,690 B2
• Filed: 12/04/2000
• Issued: 04/08/2003
• Est. Priority Date: 12/04/2000
• Status: Expired due to Term

• Current Assignee: Schlumberger Holdings Ltd. (Schlumberger NV), STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: Schlumberger Holdings Corporation (Schlumberger NV), STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Leydier, Robert Antoine, Pomet, Alain Christophe
• Primary Examiner(s): Le, Thien M.
• Assistant Examiner(s): Caputo, Lisa M.
• Application Number:
  US09/729,113
• Publication Number:
  US 20020066791A1
• Time in Patent Office: 855 Days
• Field of Search: 235/451, 235/492, 710/15, 327/108
• US Class Current: 235/451
• CPC Class Codes: G06F 13/4086 Bus impedance matching, e.g. termination

Abstract

A method and apparatus is disclosed for communicating with a host. In one embodiment, a smart card has an IC with voltage conditioning circuitry and a pull-up resistor. The smart card, when inserted in a smart card reader coupled to the host, is capable of signaling the host over a bus using the pull-up resistor selectively coupled to a voltage output of the voltage conditioning circuitry and a first output of the smart card. The voltage conditioning circuitry output is selectively coupled to the first output through the resistor, responsive to the device being powered by the bus but not transmitting. This tends to pull up the first output to the voltage level of the voltage source, which makes the smart card capable of being properly detected by the host upon the bus being driven by a host. Selectively disconnecting the pull-up resistor while the smart card is transmitting or receiving results in a more balanced differential output signal. Since the pull-up resistor and voltage conditioning circuitry supplying the proper voltage to the pull-up resistor are an integrated part of the IC, no separate contact is required to supply voltage to the resistor. This permits the smart card to be compatible with the contact configuration of certain existing smart cards, and eliminates a need for the pull-up resistor or voltage conditioning circuitry to be included in the smart card reader.

Claims

1. An apparatus for communicating with a host, comprising:

a card;

an integrated circuit (“

IC”

) affixed to the card, wherein the IC is coupled to a number of contacts, including a first output of the IC being coupled to a first one of the contacts, wherein a resistor of the IC is coupled to the first one of the contacts, and the IC includes voltage conditioning circuitry coupled to a second one of the contacts to receive a voltage supply, wherein the voltage conditioning circuitry is capable of generating an output voltage selectively coupled to the first contact, to selectively pull up the first contact to the output voltage through the resistor, so that attachment of the apparatus is capable of being detected, by the host detecting the output voltage on the first contact.

2. The apparatus of claim 1, wherein the apparatus comprises:

a switch on the IC coupled in a series circuit, the series circuit including the voltage conditioning circuitry output, the resistor and the first contact; and

control circuitry on the IC for selectively pulling up or not pulling up the first contact to the output voltage of the voltage conditioning circuitry through the resistor and the switch.

3. The apparatus of claim 2, wherein the control circuitry is capable of selecting whether to pull up the first contact to the output voltage of the voltage conditioning circuitry, responsive to the apparatus being powered.

4. The apparatus of claim 3, comprising:

a second output of the IC coupled to a third one of the contacts, wherein the control circuitry decouples the first contact from the voltage conditioning circuitry output voltage, responsive to data transfer between the apparatus and the host, so that an imbalance is reduced for signals on the first and second outputs, respectively.

5. The apparatus of claim 4, wherein the control circuitry is capable of decoupling the first contact from the resistor.

6. The apparatus of claim 1, comprising a reader having a first connector for connection to a port, and a second connector for receiving the card and electrically coupling to the contacts.

7. The apparatus of claim 6, wherein the reader has solely passive electronic components.

8. The apparatus of claim 7, wherein the second connector has passthrough contacts.

9. The apparatus of claim 1, wherein the resistor has a certain length, and is coupled to a number of impedance-value-selecting switches distributed along its length, so that the resistor is capable of being coupled through a selected one of the impedance-value-selecting switches to the first contact, for selectively varying impedance of the resistor.

10. An apparatus for communicating with a host, comprising:

a card;

an integrated circuit (“

IC”

) affixed to the card, wherein the IC is coupled to a number of contacts, including a first output of the IC being coupled to a first one of the contacts, wherein a resistor of the IC is coupled to the first one of the contacts, and the IC includes voltage conditioning circuitry coupled to a second one of the contacts for receiving a voltage supply from the host, and wherein the voltage conditioning circuitry has an output coupled to the resistor, so that attachment of the apparatus is capable of being detected by the host;

wherein a switch on the IC is coupled in a series circuit, the series circuit including the voltage conditioning circuitry output, the resistor and the first contact, and wherein the IC comprises;

control circuitry for selectively pulling up or not pulling up the first contact to the output of the voltage conditioning circuitry through the resistor and the switch; and

wherein the apparatus further comprises;

a reader, having a connector for connection to a port, and a passthrough connector for receiving the card and coupling to the contacts, wherein electrical components of the reader consist solely of passive components.

11. The apparatus of claim 10, wherein the control circuitry is capable of selectively pulling up the first contact to the output voltage of the voltage conditioning circuitry, responsive to the apparatus being powered.

12. The apparatus of claim 11, comprising:

a second output of the IC coupled to a third one of the contacts, wherein the control circuitry is capable of decoupling the first contact from the voltage conditioning circuitry output voltage, responsive to data transfer between the apparatus and the host, so that an imbalance is reduced for signals on the first and third contacts, respectively.

13. The apparatus of claim 12, wherein the control circuitry is capable of decoupling the first contact from the resistor.

14. A method for communicating with a host, comprising the steps of:

a) receiving a voltage at a first voltage level, on a first contact of a number of contacts coupled to an integrated circuit (“

IC”

), wherein the voltage is conditioned, by voltage conditioning circuitry of the IC to generate an output voltage at a second voltage level; and

b) pulling up the second contact to the second voltage level, through a resistor of the IC coupled to the voltage conditioning circuitry output voltage and the second contact, so that attachment of an apparatus that includes the IC is capable of being detected by the host.

15. The method of claim 14, wherein the second contact is pulled up to the second voltage level through a switch on the IC, responsive to the apparatus being powered.

16. The method of claim 15, comprising the step of decoupling the second voltage level from the second contact by the switch, responsive to a detach indication from control circuitry of the IC.

17. The method of claim 15 comprising the steps of:

driving or receiving a first signal by a first driver or a first receiver on the IC for transmitting to the host, the signal being asserted on the second contact;

driving or receiving a second signal by a second driver or a second receiver for transmitting to the host or receiving from the host, the signal being asserted on a third one of the contacts; and

decoupling the second voltage level from the second contact by a switch on the IC, responsive to the apparatus transmitting or receiving, to reduce an imbalance for the first and second signals.

18. The method of claim 17, comprising the step of re-connecting the second voltage level to the second contact by the switch, responsive to termination of the transmitting.

19. The method of claim 14, wherein step a) comprises the step of:

electrically coupling a connector of a reader to the contacts, for coupling the IC to the host, wherein the reader solely has passive components.

20. An apparatus for communicating with a host comprising:

an integrated circuit (“

IC”

) coupled to a first contact and having a first driver and a first receiver, so that the IC is capable of generating a first output signal to and receiving a first input signal from the first contact for communicating with a host, wherein the IC has a voltage reference, an integrated resistor and a switch coupled in series with the first contact, and the switch is capable of coupling the first voltage reference to the first contact responsive to the apparatus being powered, in order to signal attachment to the host.

21. The apparatus of claim 20, wherein the switch is capable of decoupling the voltage reference from the first contact responsive to the apparatus transmitting or receiving.

22. The apparatus of claim 20, wherein the switch is capable of decoupling the voltage reference from the first contact in order to signal detachment of the apparatus to the host.

23. The apparatus of claim 21 or claim 22, comprising:

a second contact for receiving a voltage, the second contact being coupled to voltage conditioning circuitry on the IC for generating the voltage reference from the received voltage.

24. The apparatus of claim 23, wherein the IC comprises a second driver and a second receiver, so that the IC is capable of generating a second output signal and receiving a second input signal, and the apparatus comprises a third contact coupled to the IC second output and input signals, for communicating with the host, and a fourth contact coupled to the IC, for coupling the host and the IC with an electrical common voltage, the apparatus being capable of communicating with the host through contacts of the apparatus consisting solely of the four contacts.

25. A method for communicating between an apparatus and a host comprising the steps of:

coupling a voltage reference by a switch through a resistor in an integrated circuit (“

IC”

) of the apparatus to a first contact coupled to the IC, so that the host can detect attachment of the apparatus, wherein the coupling is responsive to the IC being powered;

asserting first and second output signals by the IC, for transmitting to the host, the first signal being asserted on the first contact and the second signal being asserted on a second contact coupled to the IC; and

decoupling the voltage reference of the IC from the first contact, by the switch in the IC, wherein the decoupling is responsive to the IC transmitting or receiving.

26. The method of claim 25, wherein the IC and the contacts are affixed to a card, the method comprising the steps of:

electrically coupling the host to the IC via a passthrough connector of a reader, the reader having solely passive components, wherein the coupling includes coupling the host to the contacts for the respective first and second signals.

27. The method of claim 25 wherein the step of electrically coupling the host via the passthrough connector to the IC comprises coupling power and ground signals from the host to respective third and fourth contacts and coupled to the IC.