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Method and apparatus for limiting access to an integrated circuit (IC)

  • US 9,046,570 B2
  • Filed: 08/03/2012
  • Issued: 06/02/2015
  • Est. Priority Date: 08/03/2012
  • Status: Active Grant
First Claim
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1. A method comprising:

  • a) determining at an integrated circuit (IC) if a clock frequency of a clock signal at the IC is abnormal by virtue of being slower than a specified lower clock frequency limit;

    b) determining at the IC if the clock frequency is abnormal by virtue of being faster than a specified upper clock frequency limit;

    c) determining at the IC if the clock frequency is abnormal by virtue of the clock signal having stopped;

    utilizing at least one bandgap reference for the determining if the clock frequency is slower than the specified lower clock frequency limit and for determining if the clock frequency is faster than the specified upper clock frequency limit, wherein the utilizing the bandgap reference comprises utilizing a sampled bandgap reference, wherein the sampled bandgap reference is refreshed to maintain accuracy of the bandgap reference; and

    limiting access to the IC in response to determining the clock frequency is abnormal by at least one of a), b), and c).

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