PLA Testing Kalpak(m314320)
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Transcript of 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
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!. "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#$+%& circuit
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"ntroduction
• PLA descried y ) -atri P / 0 A,% 1 – 2here A 3 ' n 0representing A#$
Array1
% 3 ' k 0representing %& Array1• ', n, k are inputs product ter's and outputs
• this -atri is called as PLA4s
personality
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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
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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!
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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
• $isappearance fault
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*ault -odels
• -ost co''on 3 stuck at *ault
s)a) or s)a)7 can occur at any wire within inputoutput lines it lines and product lines.
•
Stuck)at faults alone cannot 'odel allphysical defects in PLAs
• New class of fault named ‘crosspoint’ faultscan occur in PLA
• crosspoint fault is either an extra or a
missing connection at a crosspoint in theA#$ or %& array of a PLA
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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 $isappearance
Product lineand output
line
;orrespondingi'plicant
disappears inoutput
• -issing crosspoint e<ui(alent to stuck faults
• 5tra connections cannot e 'odeled y
stuck faults
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• there are (2n + k)m possile singlecrosspoint faults and 3 di:erent singleand 'ultiple crosspoint faults.
• -ultiple faults are co''on in PLAs.• *aults in PLA
– -ultiple stuck faults
–
-ultiple crosspoint faults – ;o'inations of these faults
• PLA4s can e 'odeled as %& or A#$ridging faults ecause either a =high= or=low= (oltage will do'inate.
•
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!.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.
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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.