Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Random Access Memory Redundancy Via a Programmable Logic Array

IP.com Disclosure Number: IPCOM000041218D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Bula, O: AUTHOR [+4]

Abstract

A programmable logic array (PLA) is programmed to decode an address input of a random access memory (RAM) chip. When selected, the PLA routes data to and from data input/output (I/O) pins to storage cells which are activated by the decoded line of the PLA.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 1

Random Access Memory Redundancy Via a Programmable Logic Array

A programmable logic array (PLA) is programmed to decode an address input of a random access memory (RAM) chip. When selected, the PLA routes data to and from data input/output (I/O) pins to storage cells which are activated by the decoded line of the PLA.

Referring to the figure, latches 2 and 4 store column and row addresses, respectively, which come from input to RAM address decode circuits. The data is presented to the AND portion of the array, 6 and 8, respectively. When the AND array is programmed, any product term which coincides with both the 2 and 4 latches produces an active data select (DS) signal. This DS signal is recognized by DOT OR 10, and multiplexor 12 switches chip I/O connections 18 from main RAM storage 14 to redundancy storage 16. The DS signal also provides a decoded address input to redundancy storage RAM 16. Read/write line R/W directs the flow of information to redundancy storage RAM 16, just as it does in the main RAM storage 14.

Yield of good RAM devices is sufficiently high that testing of the small number of redundant bits in storage 16 becomes unnecessary.

Disclosed anonymously.

1