pla testing kalpak(m314320)

7/16/2019 PLA Testing Kalpak(m314320)

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PLA Testing

Under guidance of,

Prof. P. P. Gundewar

By,

Kalpak Shaha



!. "ntroduction

• PLA consist of • "nput decoder

• A#$ Array

• %& Array

• PLA i'ple'ents Two logic le(els• #A#$)#A#$

•

#%&)#%&• *or si'plicity we consider an

A#$+%& circuit



"ntroduction

• PLA descried y ) -atri P / 0 A,% 1 – 2here A 3 ' n 0representing A#$

Array1

% 3 ' k 0representing %& Array1• ', n, k are inputs product ter's and outputs

• this -atri is called as PLA4s

personality



A PLA structure with itdecoders

• ' n 'atri )A#$ array

• ' k 'atri )%& array

• "ntersection ofit or outputline 3 crosspoint – At each

crosspoint atransistor eists

– And ifconnection isn4twanted disale

transistor



5a'ple

• *or an A#$ array – ) 6i , 7 3 6i

– ) $on4t care

0connection asent1

•

*or %& array – ) connection present

– 7 ) connection asent

• PLA showni'ple'ents function

f / 6 + 686! + 6968

f / 686! + 669686! +6968 + 669686!



PLA Testing prole's

• PLA testing an i'portant issue. Though PLAs o:er 'any ad(antages,they also present new testing

prole's. – Fault Models

• Shrinkage fault

•

Growth fault• Appearance fault

• $isappearance fault



*ault -odels

• -ost co''on 3 stuck at *ault

s)a) or s)a)7 can occur at any wire within inputoutput lines it lines and product lines.

•

Stuck)at faults alone cannot 'odel allphysical defects in PLAs

• New class of fault named ‘crosspoint’ faultscan occur in PLA

• crosspoint fault is either an extra or a

missing connection at a crosspoint in theA#$ or %& array of a PLA



Sr.No.

Fault Extraconnectionbetween

Missingconnectionbetween

Cause

Shrinkage Bit line andproduct line

"ncludes additional input

9 Growth Bit line andproduct line

eco'esindependent ofadditional input

8 Appearance Product line

and outputline

;orresponding

i'plicant appearsin output

8 $isappearance

Product lineand output

line

;orrespondingi'plicant

disappears inoutput

• -issing crosspoint e<ui(alent to stuck faults

• 5tra connections cannot e 'odeled y

stuck faults



• there are (2n + k)m possile singlecrosspoint faults and 3 di:erent singleand 'ultiple crosspoint faults.

• -ultiple faults are co''on in PLAs.• *aults in PLA

– -ultiple stuck faults

–

-ultiple crosspoint faults – ;o'inations of these faults

• PLA4s can e 'odeled as %& or A#$ridging faults ecause either a =high= or=low= (oltage will do'inate.

•



!.9.9 Prole's with Traditional TestGeneration -ethods

• PLA corresponds to two)le(el su')of)productcircuit with input in(erter

• n-%S technology it is often i'ple'ented y twole(els of #%&)#%& gates with output in(erters

• %ne way to generate tests for a PLA is ?rst tocon(ert the PLA into a two)le(el gate circuit andthen to ?nd tests for stuck faults in the=e<ui(alent= gate circuit.

• -any traditional algorith's eist and these'ethods share two serious prole's.

• two)le(el circuit is logically e<ui(alent to the PLA,as far as fault eha(iour is concerned, they are note<ui(alent.



Prole's with Traditional Test

Generation -ethods

• etra crosspoint fault in the A#$ array,cannot e 'odeled as a stuck fault in thegate circuit.

•high fault co(erage is not guaranteed

• traditional test generation algorith's arenot always e:ecti(e for PLAs ecause PLAsha(e high fanin ,fanout and redundancy.

• Although ehausti(e testing is not a:ectedy these factors, it eco'es less applicaleas the si@e of the PLA increases.



• Thank you

pla testing kalpak(m314320)

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