Abstract
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, en- durance, organization, density or protocol of the mem- ory array of the device. The user selected configuration is made permanent and inaccessible for change by pro- gramming associated normally reversible configuration fuses which are rendered incapable of being repro- grammed (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 opera- tion 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 conse- quence of automatic simultaneous programming of the lockout fuse and configuration fuses at any time after shipment of the device from the factory.