Microprocessor apparatus and method for securing a programmable 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 a legal level;
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 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 an illegal level regardless of whether said feature fuse is blown; and
a blow controller, coupled to a fuse array, configured to receive a voltage, and configured to blow a selected fuse within said fuse array responsive to a value of said voltage, wherein blowing of said selected fuse is allowed only when the extended JTAG operations are enabled.
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Accused Products
Abstract
An apparatus for precluding the use of extended JTAG operations, including a JTAG control chain, a feature fuse, a level sensor, an access controller, and a blow controller. The JTAG control chain enables/disables the extended JTAG operations. The feature fuse indicates whether the extended JTAG features are to be disabled. The level sensor monitors an external voltage signal, and indicates that the external voltage signal is at a legal level. The access controller determines if the feature fuse is blown, and directs the JTAG control chain to disable the extended JTAG operations if the feature fuse is blown, and directs 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. The blow controller receives a voltage, and blows a selected fuse within a fuse array responsive to a valve of the voltage.
15 Citations
21 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 a legal level; 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 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 an illegal level regardless of whether said feature fuse is blown; and a blow controller, coupled to a fuse array, configured to receive a voltage, and configured to blow a selected fuse within said fuse array responsive to a value of said voltage, wherein blowing of said selected fuse is allowed only when the extended JTAG operations are enabled. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus in an integrated circuit for precluding the use of extended JTAG operations, the apparatus comprising:
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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 a legal level;
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 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 an illegal level regardless of whether said feature fuse is blown; anda blow controller, coupled to a fuse array, configured to receive a voltage, and configured to blow a selected fuse within said fuse array responsive to a value of said voltage, wherein blowing of said selected fuse is allowed only when the extended JTAG operations are enabled. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. 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 the feature fuse is blown, and directing a JTAG control chain to disable the extended JTAG operations; second determining if an external voltage signal is at a legal level; disabling the extended JTAG operations if the feature fuse is blown, and directing the JTAG control chain to disable the extended JTAG operations if the external voltage is at an illegal level regardless of whether the feature fuse is blown; and receiving a voltage, and blowing a selected fuse within a fuse array responsive to a value of the voltage, wherein said blowing is allowed only when the extended JTAG operations are enabled. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification