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Three State Associative Cross Coupled SCR Cell

IP.com Disclosure Number: IPCOM000076203D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Schuenemann, CL: AUTHOR

Abstract

The cross-coupled silicon-controlled rectifier (SCR) cell has three storage states: "0", "1", and "neutral". In the neutral state both SCR's are OFF.

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Three State Associative Cross Coupled SCR Cell

The cross-coupled silicon-controlled rectifier (SCR) cell has three storage states: "0", "1", and "neutral". In the neutral state both SCR's are OFF.

The drawing shows the circuit diagram of the cell wired for application in an associative array structure. The SCR's are operated in a DC stable state. For select and read/write operations, two symmetrical transistors T1 and T2 are included in the cell.

In an associative memory a word is selected when the associative cells match the applied bit combination. In this case no current on word line WL 1 is indicative of "match". Match is obtained when bit line B0 is on high potential and SCR 1 is OFF, or when bit line B1 is on high potential and SCR2 is OFF, or when both SCR's are OFF. The P3-layer of PNP transistors T1 and T2, respectively, operates in each case as an emitter and the P4-layer as a collector. Word line WL2 is prevented from drawing current from the collector, since base N1 is not driven by the connected SCR. In the case of a mismatch, since base current is permitted to flow into SCR, transistors T1 and T2, respectively, are driven by the connected SCR, while collector current flows into word line WL2.

Reading is performed by applying a positive pulse to word line WL1. In this case the P4-layer of transistors T1 and T2, respectively, acts as an emitter. When the connected SCR is ON, the related transistor is driven and the bit line draws collector current. Wi...