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Browse Prior Art Database

Pipe Tolerant Inverted Transistor Read Only Store

IP.com Disclosure Number: IPCOM000084439D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Buckley, F: AUTHOR [+2]

Abstract

Referring to Figs. 1a and 1b, an inverted transistor (MTL) read-only store (ROS) is built with isolated word lines W. Each word line (normal collector region) contains a base diffusion along its entire length, which is maintained at a constant 0.9 volt for all word lines in the entire array. A word line 2, for example, is selected by turning on word line driver D2 and leaving all other drivers off. The presence of bit B21 is sensed by bit line receiver R1 when the bit line current i exceeds I.

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Pipe Tolerant Inverted Transistor Read Only Store

Referring to Figs. 1a and 1b, an inverted transistor (MTL) read-only store (ROS) is built with isolated word lines W. Each word line (normal collector region) contains a base diffusion along its entire length, which is maintained at a constant 0.9 volt for all word lines in the entire array. A word line 2, for example, is selected by turning on word line driver D2 and leaving all other drivers off. The presence of bit B21 is sensed by bit line receiver R1 when the bit line current i exceeds I.

A pipe is a collector emitter short and can only occur if a collector is present. Thus, when D2 is on, a pipe at B22 cannot occur and pipes at B21 and B23 reinforce the desired current i. Further, a pipe at B32, when D2 is on, causes no error because D3 is off and the pipe current path is broken.

There exists two sneak paths for signal currents. In the first (Fig. 2), a pipe between a word and a bit line will tend to pull the word line negative when the bit line is negative. This current would tend to turn on any bits connected to this word line.

The second path (Fig. 3) occurs when the transistor comprising a bit is allowed to saturate which forward biases the base-collector junction. Since all bases are at the same potential, the base-collector junctions of all other bits connected to the bit line are forward biased and the collectors act as emitters. Current is then drawn from the other word lines and would tend to turn o...