Method of preventing unauthorized reproduction of a transmission code

• US 6,046,680 A
• Filed: 06/15/1994
• Issued: 04/04/2000
• Est. Priority Date: 06/15/1994
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Davis, Gregory B., Soenen, Eric G.
• Primary Examiner(s): ZIMMERMAN, BRIAN A
• Application Number:
  US08/260,148
• Time in Patent Office: 2,120 Days
• Field of Search: 340/825.31, 340/825.34, 340/825.52, 340/825.69, 340/825.72, 380/3, 380/4
• US Class Current: 340/5.23
• CPC Class Codes: G07C 2009/00793 by Hertzian waves
• CPC Class Codes: G07C 2009/00849 programming by learning
• CPC Class Codes: G07C 9/00309 operated with bidirectional data transmission between data carrier and locks
• CPC Class Codes: G08C 19/28 using pulse code

Abstract

An integrated circuit (IC) configurable as transmitter/receiver includes a method of preventing unauthorized learning and reproduction of an access code as a security measure. When the IC is configured as a receiver and placed in the learn mode, a flag is set in a memory of a microcontroller. If later configured as a transmitter, the microcontroller checks the flag upon power up and if the flag is set, the stored code is randomized so transmission of it is impossible.

Claims

1. A method for preventing unauthorized learning and reproduction of an access code in a combined receiver/transmitter system comprising the steps of:

setting a flag in a memory of an integrated circuit upon the first time the integrated circuit is placed in a learn mode while configured as a receiver; and

checking the flag if the integrated circuit is later configured as a transmitter; and

modifying the code if the flag is set.

2. The method of claim 1 wherein the step of setting a flag in a memory of an integrated circuit includes setting a flag in a memory of a microcontroller.

3. A method of preventing unauthorized learning and reproduction of an access code in an integrated circuit configurable as a receiver and configurable as a transmitter, comprising the steps of:

configuring an integrated circuit as a receiver;

receiving a transmitted access code;

storing the access code in the integrated circuit configured as a receiver;

setting a flag in the integrated circuit configured as a receiver;

reconfiguring the integrated circuit as a transmitter;

checking the flag; and

denying transmission of the access code if the flag is set.

4. The method of claim 3 wherein the step of checking the flag is performed by a microcontroller.

5. The method of claim 4 wherein the step of denying transmission of the access code includes the step of resetting the stored access code.