Method for communicating with a plurality of contactless data carriers and contactless data carrier for use therein

• US 6,354,500 B1
• Filed: 09/02/1999
• Issued: 03/12/2002
• Est. Priority Date: 11/21/1996
• Status: Expired due to Term

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Research
• Inventors: De Champs, Paul, Gercekci, Anil
• Primary Examiner(s): Lee, Michael G.
• Assistant Examiner(s): FRANKLIN, JAMARA ALZAIDA
• Application Number:
  US09/308,605
• Time in Patent Office: 922 Days
• Field of Search: 235/492, 235/451, 235/375, 235/379-384, 235/487, 340/10-- 1
• US Class Current: 235/451
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10059 transponder driven

Abstract

A method of communicating with a plurality of contactless data carriers and a contactless data carrier for use in communicating with a base station. The method of communicating includes the base station transmitting a wake up signal for a plurality of contactless data carriers which are in a wait state. Then, the data carriers exit the wait state and transmit identity information to the base station in a time slot that is randomly self-assigned. The base station registers the identity information by polling the registered data carriers and initiates dialogue with registered data carriers in an order determined by the randomly self-assigned time slots of the registered data carriers. The method of communication helps to avoid the problem of data collision that often occurs when multiple contactless data carriers or smart cards operate in the field of a single base station or card reader.

Claims

1. A method for communicating with a plurality of contactless data carriers, comprising:

a base station transmitting a power signal;

a data carrier powering itself up in response to the transmitted power signal, and entering a wait state;

the base station transmitting a first start up signal for waiting data carriers;

the waiting data carriers exiting the wait state in response to the wake up signal and transmitting identity information in a time slot that is randomly self-assigned;

the base station registering the identity information by polling the registered data carriers and initiating dialogue with registered data carriers in an order determined by the random self-assigned time slots of the registered data carriers;

the base station completing dialogue with a first registered data carrier;

the first registered data carrier shutting down for a remaining time of a communication session;

the base station transmitting a second start up signal to initiate dialogue with a next registered data carrier, the base station initiating dialogue with all of the registered data carriers to complete the communication session; and

wherein the first and second start up signals are distinguishable, the first start up signal being used to initiate a communication session with any one of the data carriers, the second start up signal being used to continue the communication session with only registered data carriers.

2. The method of claim 1, wherein the step of the base station initiating dialogue with the next registered data carrier includes determining which of the registered data carriers has a next self-assigned time slot to become the next registered data carrier.

3. The method of claim 1, wherein the base station initiates dialogue with all of the registered data carriers to complete the communication session.

4. The method of claim 3, wherein a next communication session is started by the base station transmitting a next wake up signal.

5. The method of claim 1 wherein the step of the base station initiating dialogue with registered data carriers further includes:

the base station resending the identity information of a first data carrier;

the first data carrier recognizing the identity information and sending an acknowledgment message to the base station; and

the base station proceeding with carrying out a transaction with the first data carrier upon receipt of the acknowledgment message.

6. The method of claim 5, further comprising:

the first data carrier reassigning itself a new time slot if the acknowledgment message is not received by the base station; and

the first data carrier waiting for a new wake up signal from the base station.

7. A contactless data carrier for communication with a base station comprising:

means for receiving a power signal transmitted by the base station;

means for powering up the data carrier in response to receipt of the power signal, and entering a wait state;

means for receiving a first start up signal transmitted by the base station at an initiation of a communication session;

means for exiting the wait state in response to receipt of the first start up signal;

means for determining a randomly self-assigned time slot, and transmitting identity information in the randomly self-assigned time slot;

means for receiving a second start up signal transmitted by the base station during the communication session, said second start up signal being distinguishable from the first start up signal, the first start up signal being used to initiate a communication session with any one of the data carriers and the second start up signal being used to continue communication with only registered data carriers; and

means for conducting a dialogue with the base station on receipt of an individually identified message therefrom.

8. The data carrier of claim 7, further comprising:

means for shutting down following the completion of the dialogue from the base station.

9. The data carrier of claim 7, further comprising:

means for recognizing identity information sent back from the base station; and

means for transmitting an acknowledgment message to the base station.

10. The data carrier of claim 9, further comprising:

means for reassigning itself a new time slot if the acknowledgment message is not received by the base station.