Apparatus and method for tamper protection of a microprocessor fuse array
First Claim
1. An apparatus in an integrated circuit for precluding the use of extended JTAG operations, the apparatus comprising:
- a JTAG control chain, configured to enable/disable the extended JTAG operations;
a feature fuse, configured to indicate whether the extended JTAG features are to be disabled;
a level sensor, configured to monitor an external voltage signal, and configured to indicate that said external voltage signal is at an illegal level; and
an access controller, coupled to said feature fuse, said level sensor, and said JTAG control chain, configured to determine if said feature fuse is blown, and configured to direct said JTAG control chain to disable the extended JTAG operations if said external voltage signal is at said illegal level regardless of whether said feature fuse is blown.
1 Assignment
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Accused Products
Abstract
An apparatus in an integrated circuit for precluding the use of extended JTAG operations. The apparatus has a JTAG control chain, a feature fuse, a level sensor, and an access controller. The JTAG control chain is configured to enable/disable the extended JTAG operations. The feature fuse is configured to indicate whether the extended JTAG features are to be disabled. The level sensor is configured to monitor an external voltage signal, and configured to indicate that the external voltage signal is at an illegal level. The access controller is coupled to the feature fuse, the level sensor, and the JTAG control chain, and is configured to determine if the feature fuse is blown, and is configured to direct the JTAG control chain to disable the extended JTAG operations if the external voltage signal is at an illegal level regardless of whether the feature fuse is blown.
18 Citations
24 Claims
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1. An apparatus in an integrated circuit for precluding the use of extended JTAG operations, the apparatus comprising:
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a JTAG control chain, configured to enable/disable the extended JTAG operations; a feature fuse, configured to indicate whether the extended JTAG features are to be disabled; a level sensor, configured to monitor an external voltage signal, and configured to indicate that said external voltage signal is at an illegal level; and an access controller, coupled to said feature fuse, said level sensor, and said JTAG control chain, configured to determine if said feature fuse is blown, and configured to direct said JTAG control chain to disable the extended JTAG operations if said external voltage signal is at said illegal level regardless of whether said feature fuse is blown. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus in an integrated circuit for precluding the use of extended JTAG operations, the apparatus comprising:
a microprocessor, comprising; a JTAG control chain, configured to enable/disable the extended JTAG operations; a feature fuse, configured to indicate whether the extended JTAG operations are to be disabled; a level sensor, configured to monitor an external voltage signal, and configured to indicate that said external voltage signal is at an illegal level; and an access controller, coupled to said feature fuse, said level sensor, and said JTAG control chain, configured to determine if said feature fuse is blown, and configured to direct said JTAG control chain to disable the extended JTAG operations if said external voltage signal is at said illegal level regardless of whether said feature fuse is blown. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method for precluding the use of extended JTAG operations in an integrated circuit, the method comprising:
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via blowing a feature fuse that is disposed within the integrated circuit, indicating that extended JTAG operations are to be disabled; first determining if an external voltage signal is at an illegal level; second determining if the feature fuse is blown; if the external voltage signal is at the illegal level, directing a JTAG control chain to disable the extended JTAG operations; and if the external voltage signal is at a legal level, and the feature fuse is blown, directing a JTAG control chain to disable the extended JTAG operations. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification