| 摘要 |
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. |
