Scan and boundary scan disable mechanism on secure device
First Claim
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1. A circuit comprising:
- a plurality of logic modules configured to (i) store a plurality of values and (ii) force said values in storage to a plurality of predetermined values respectively while a scan mode signal is active; and
a security module configured to (i) disable a scan capability to read said values through a first scan chain while in a non-lowest security mode of at least three security modes and (ii) enable said scan capability to read said values through said first scan chain while in a lowest security mode of said at least three security modes.
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Abstract
A circuit generally comprising a logic module and a security module is disclosed. The logic module may be configured to set a plurality of values to a plurality of predetermined values respectively while in a scan mode. The security module may be configured to (i) disable a scan capability of the values while in a non-lowest security mode of at least three security modes and (ii) enabling the scan capability while in a lowest security mode of the security modes.
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Citations
20 Claims
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1. A circuit comprising:
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a plurality of logic modules configured to (i) store a plurality of values and (ii) force said values in storage to a plurality of predetermined values respectively while a scan mode signal is active; and a security module configured to (i) disable a scan capability to read said values through a first scan chain while in a non-lowest security mode of at least three security modes and (ii) enable said scan capability to read said values through said first scan chain while in a lowest security mode of said at least three security modes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of operating a circuit, comprising the steps of:
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(A) storing a plurality of values; (B) disabling a scan capability to read said values through a scan chain while in a non-lowest security mode of at least three security modes; (C) forcing said values in storage to a plurality of predetermined values respectively while a scan mode signal is active; and (D) enabling said scan capability to read said values through said scan chain while in a lowest security mode of said at least three security modes. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A circuit comprising:
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means for (i) disabling a scan capability to read a plurality of values through a scan chain while in a non-lowest security mode of at least three security modes and (ii) enabling said scan capability to read said values through said scan chain while in a lowest security mode of said at least three security modes; and means for (i) storing said values and (ii) forcing said values in storage to a plurality of predetermined values respectively while a scan mode signal is active.
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Specification