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A BIDIRECTIONAL DATA PATH FOR AN EMBEDDED MEMORY

IP.com Disclosure Number: IPCOM000007347D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2002-Mar-18
Document File: 3 page(s) / 107K

Publishing Venue

Motorola

Related People

David Porter: AUTHOR [+2]

Abstract

Die cost economics require high-density mem- ories to utilize array redundancy, which invokes the necessity to physically locate defective memory cells in an array, usually referred to as bitmapping. For a typical memory, bitmapping capability is an inher- ent fact, since memory locations and the data therein are externally accessable. In the case ofan imbedded memory, however, data is supplied for internal DSP, a design technique which allows data to be externally accessable must be implemented.

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MOTOROLA Technical Developments Volume 24 March 1995

A BIDIRECTIONAL DATA PATH FOR AN EMBEDDED MEMORY

by David Porter and Bruce Engles

the BDL exports memory data to the test data block, as shown in Figure 3.

  Referring to Figure 4, in the normal mode of operation, data is passed from the memory to ALU by turning on transistor Ml and turning off transis- tor M2. Redundant data is passed from the redun- dant memory to the ALU by turning off transistor Ml and turning on transistor M2. Logic gates NRl and ND1 are shared across several different data paths, the number being determined by how many data paths are present in one redundant element. Logic gates NRl and ND1 provide the means to address a failing column and allow redundant data to be used instead. In the normal mode of opera- tion, the BLOCKB and COLB lines carry informa- tion about which, ifany memory data lines have been replaced with the redundant memory The redun- dant memory drives the BDL with redundant data.

  In the test mode of operation, the BDL exports memory data to the TEST DATA OUT BLOCK by turning on M2 of the addressed mux and turning on all Ml transistors by way of the TESTB input to NDl, while the tristateable driver in the redun- dant memory is tristated, allowing the addressed mux to drive the BDL. The BLOCKB and COLB lines carry address information in the test mode ofopera- tion. In the second case, the BDL still exports mem- ory data, but the test data out block chooses data from the RDL.

BACKGROUND

  Die cost economics require high-density mem- ories to utilize array redundancy, which invokes the necessity to physically locate defective memory cells in an array, usually referred to as...