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Apparatus and method for sensitive circuit protection with set-scan testing

  • US 5,357,572 A
  • Filed: 09/22/1992
  • Issued: 10/18/1994
  • Est. Priority Date: 09/22/1992
  • Status: Expired due to Term
First Claim
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1. An electrical circuit having a plurality of subcircuits and a set-scan test input for testing said subcircuits in a set/scan test mode, some of said subcircuits being sensitive subcircuits protected from reverse engineering, wherein the improvement comprises:

  • selectable means, coupled to at least some of said sensitive circuits, for inhibiting set/scan test access to said at least some of said sensitive subcircuits, andmeans for actuating said selectable means, coupled between said subcircuits and said selectable means, to inhibit set/scan access to said sensitive subcircuits while permitting set/scan access to the other subcircuits.

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