Method for programming permanent calibration information at final test without increasing pin count

Abstract

A System and method for calibrating a chip after packaging including providing a packaged chip, providing programmable non-volatile storage having a plurality of non-volatile storage elements in the chip and providing a volatile storage having a plurality of volatile storage elements in the chip with one volatile storage element associated with one non-volatile storage element. The chip includes circuitry responsive to a predetermined signal to permit the non-volatile storage to be programmed in accordance with data stored in the volatile storage and to a predetermined signal to prevent external alteration of the non-volatile storage. The non-volatile storage is preferably a plurality of fuses. The volatile storage is preferably a shift register. The circuitry in the chip includes a bistable device responsive to the predetermined signal to assume a first condition to permit the non-volatile storage to be programmed and responsive to the alteration of the predetermined signal to assume a second condition which does not allow alteration of data. The system further includes a non-volatile storage element settable to one of a first or a second condition and preset to the first condition, the circuitry in the chip responsive to the first condition to permit the non-volatile storage to be programmed in accordance with data stored in the storage and responsive to the second condition to prevent external alteration of the non-volatile storage. The condition of the non-volatile element determines whether or not the first state (program) of the bistable device can be entered.

Dependencies are inferred from the claim text.