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Technique for Implementing Control Logic for Self-Test Operations

IP.com Disclosure Number: IPCOM000036305D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 61K

Publishing Venue

IBM

Related People

Jaber, TK: AUTHOR

Abstract

This article describes a piece of control logic capable of providing necessary control signals needed to carry a logic self-test operation from start until end without any control over the chip clocks.

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Technique for Implementing Control Logic for Self-Test Operations

This article describes a piece of control logic capable of providing necessary control signals needed to carry a logic self-test operation from start until end without any control over the chip clocks.

Consider a chip whose Level Sensitive Scan Design (LSSD)-compatible Shift Register Latches (SRLs) are configured in a STUMPS (Self- Test Using Multiple Parallel Signature) Architecture configuration. See Fig. 1.

For the sake of simplicity assume that no arrays exist on the chip and that a typical self-test event is defined as AB AB AB. . . . . . . . AB CB.

(Image Omitted)

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An AB is a term used to describe a scan cycle on the chip. During a scan cycle a typical SRL receives data through its Scan port. See Fig. 2.

A select signal(s) (also called scan gate) selects between (I) and (D) pins as data pins to the L1 latch.

The B clock (or L2 clock) transfers data from the output of the L1 latch to the L2 latch.

A CB is a term used to describe a system cycle. During a system cycle the
(D) port of the L1 latch is selected and the B clock (or the L2 clock) transfers data to the L2 latch.

A number of AB cycles is needed to scan data into the whole length of the longest scan channel. Following that, a CB cycle would capture the chip response to the scan vector and store it back into the SRLs via the D-ports. To compress the response data, the scan channel needs to be unloaded (scanned out) into the Multiple Input Signature Register (MISR), and as the channels are being unloaded and compressed into the MISR, a new random data vector...