Patent ID: 8429471

Claim:
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.