Pseudo random number generator

• US 6,314,440 B1
• Filed: 09/22/1998
• Issued: 11/06/2001
• Est. Priority Date: 05/13/1996
• Status: Expired due to Term

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Ovard, David K., Tuttle, John R., Rotzoll, Robert R., Tuttle, Mark E., Lowrey, Tyler, Higgins, Brian P., Yu, Shu-Sun, Devereaux, Kevin M., Pax, George E., OʼToole, James E.
• Primary Examiner(s): NGO, CHUONG D
• Application Number:
  US09/158,529
• Time in Patent Office: 1,141 Days
• Field of Search: 708/250, 708/251, 708/252, 708/253, 708/254, 708/255, 708/256, 713/320, 713/322
• US Class Current: 708/250
• CPC Class Codes: G06K 19/0707 the arrangement being capable of collecting energy from external energy sources, e.g. thermocouples, vibration, electromagnetic radiation G06K19/0702 takes precedence
• CPC Class Codes: G06K 19/0712 the arrangement being capable of triggering distinct operating modes or functions dependent on the strength of an energy or interrogation field in the proximity of the record carrier active means for hindering electromagnetic reading or writing G06K19/07336
• CPC Class Codes: G06K 19/0716 at least one of the integrated circuit chips comprising a sensor or an interface to a sensor
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07758 arrangements for adhering the record carrier to further objects or living beings, functioning as an identification tag
• 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
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H03L 7/0995 the oscillator comprising a ring oscillator
• CPC Class Codes: H03L 7/148 said digital means comprising a counter or a divider

Abstract

A radio frequency identification device comprises an integrated circuit including a receiver, a transmitter, and a microprocessor. The receiver and transmitter together define an active transponder. The integrated circuit is preferably a monolithic single die integrated circuit including the receiver, the transmitter, and the microprocessor. Because the device includes an active transponder, instead of a transponder which relies on magnetic coupling for power, the device has a much greater range.

Claims

1. A pseudo random number generator comprising:

a linear feedback shift register switchably operable in a first mode, and in a second mode wherein the shift register consumes more power than in the first mode.

2. A method of generating a pseudo random number, the method comprising:

providing a linear feedback shift register;

providing an oscillator which generates clock signals used by the linear feedback shift register for shifting; and

providing a first power level to the oscillator when a pseudo random number is required, and providing a second power level, lower than the first power level, to the oscillator at other times.

3. A method of generating a pseudo random number, the method comprising:

providing a linear feedback shift register;

providing an oscillator which generates clock signals used by the linear feeback shift register for shifting; and

operating the oscillator at a first frequency in response to a request for a pseudo random number, and operating the oscillator at a second frequency lower than the first frequency after the pseudo random number is generated.

4. A method in accordance with claim 3 and further comprising supplying power to the oscillator from a thermal voltage generator to cause the oscillator to operate at the second frequency.

5. A system comprising:

a microprocessor operating at a frequency;

a linear feedback shift register operable in a low power mode, wherein the shift register operates at a frequency below the frequency of the microprocessor, and a high power mode wherein the shift register consumes more power than in the low power mode, operates at the frequency of the microprocessor, and shifts data into the microprocessor.

6. A radio frequency identification device comprising:

an integrated circuit including a receiver, a transmitter, a thermal voltage generator, a microprocessor operating at a frequency, a linear feedback shift register operable in a low power mode, wherein the shift register operates at a frequency below the frequency of the microprocessor, and a high power mode wherein the shift register consumes more power than in the low power mode, operates at the frequency of the microprocessor, and shifts data into the microprocessor, an oscillator supplying clock signals to the shift register, and current mirrors supplying current to each stage of the shift register, the current mirrors being referenced to the thermal voltage generator when the shift register is in the low power mode, and, when the shift register is in the high power mode, connected to a supply voltage potential greater than the potential provided by the thermal voltage generator.

7. A method of generating a pseudo random number, the method comprising:

providing a thermal voltage generator, a linear feedback shift register, an oscillator supplying clock signals to the shift register, and current mirrors supplying current to each stage of the shift register;

referencing the current mirrors to the thermal voltage generator when no pseudo random number is required; and

connecting the current mirrors to a supply voltage potential greater than the potential provided by the thermal voltage generator when a pseudo random number is required.