| 摘要 |
The usability of an electrically erasable programmable semiconductor memory device is assured after shipment from the factory despite implementing the device with a user option to selectively configure the security, endurance, organization, density or protocol of the memory array of the device. The user selected configuration is made permanent and inaccessible for change by programming associated normally reversible configuration fuses which are rendered incapable of being reprogrammed (reversed) thereafter by the automatic and simultaneous programming of a lockout fuse. Final testing of the device at the factory is permitted by an override of the lockout fuse during testing of the operation of the configuration fuses, and, when the testing is completed, returning, under program control, all fuses to a default condition in which the configuration fuses are limited to one-time programmability as a consequence of automatic simultaneous programming of the lockout fuse and configuration fuses at any time after shipment of the device from the factory.
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