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United States Patent 4,132,904
January 2, 1979

Volatile/Non-Volatile Logic Latch Circuit
Eliyahou Harari

Filed July 28, 1977
Image of US PATENT 4,132,904

Abstract of the Disclosure

There is described a logic element employing fixed threshold and variable thresh old transistors electrically connected together in a unique manner to form a lat ch. The latch can be made to retain data by keeping certain internal nodes at a high or low voltage level. As such it acts as an ordinary semiconductor memory latch, whose data can be changed by externally overriding the internal voltage levels of the latch cell. The novel results of the cell described are achieved by replacing one or several of the transistors in the latch by specially constructed transistors, whose threshold voltage can be raised or lowered upon application of a relatively high voltage pulse between their gate and substrate. By application of such a high voltage pulse, the data stored in the latch can be translated into controlled threshold shifts of the variable threshold transistors, which uniquely represent the initial latch state. Therefore, if power is removed and then returned, the latch will always settle into a state dictated by the final state that existed in the latch before the high voltage pulse was applied. In this way the variable threshold elements of the latch make it a non-volatile memory element. It can be used either as a read/write memory, using its latch property, or as a read only memory, using the variable threshold transistors to cause it to always latch in a predetermined manner.
Figure descriptions: cover graphic

  • a latch circuit made in accordance with the present invention and having FATMOS transistors as its drivers.

 Citations [54]:
  
3,636,530 01/1972 Mark et al 3,774,087 11/1973 Pepper 3,831,155 08/1974 Tamaru et al 3,836,894 09/1974 Cricchi 3,845,327 09/1974 Cricchi 4,016,588 04/1977 Ohya et al 4,019,197 04/1977 Lostroh et al 4,030,081 06/1977 Horninger 4,037,242 07/1977 Gosney 4,044,343 08/1977 Uchida 4,070,655 01/1978 Schurmeyer et al
National Museum of American History
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