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AC Stable Associative Memories

IP.com Disclosure Number: IPCOM000080914D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 33K

Publishing Venue

IBM

Related People

Pricer, WD: AUTHOR

Abstract

This field-effect transistor (FET) circuit provides an associative memory function in simple circuitry fabricated from conventional metal-oxide semiconductor (MOS) technology.

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AC Stable Associative Memories

This field-effect transistor (FET) circuit provides an associative memory function in simple circuitry fabricated from conventional metal-oxide semiconductor (MOS) technology.

Array logic has become one of the primary solutions to the design of large- scale integrated logic. The logic functions are usually assumed to be reprogrammable. A highly desirable feature in array logic is the ability to recognize prime implicants. This contributes significantly to the bit efficiency of array logic, because only a very few of the possible logical combinations show up as terms in any meaningful equation.

The proposed cells are the AC stable variety and hence have to be periodically refreshed. They differ from the destructive read storage cells in that they may be interrogated without losing information. This is a necessary feature of associative memories.

The operation of the circuit in Fig. 1 can be illustrated with the following voltage levels. All devices are assumed to be N channel. At rest, the Word Write line is at ground, Word Sense line, B0 and B1 lines are all at +5 volts. To write, the Word Write line is pulsed from the rest position to be equal to, or greater than, 7 volts. Coincident with this pulse, either B0 or B1, is raised to +10 volts. To interrogate either B0 or B1 is pulsed to +10 volts. If a mismatch between the stored information and the search "key" is found, either T1 or T4 will conduct in the source-follower mode producing a mismatch signal on the Word Sense line, thereby disqualifying that word. The cell may be read by pulsing Word Sense to ground. Either T1 or T4 will then conduct in grounded source mode, thereby indicating the state of the cell.

It should be noted that the cell consists of...