0 scan chain reorder

8/12/2019 0 Scan Chain Reorder

1/48

NCHUCS 1

Scan Chain Reorder

Sying-Jyan Wang

Department of Computer Science

National Chung-Hsing University


2/48

NCHUCS 2

utline

vervie!

Scan chain order" does it matter#

Cluster-$ased reordering for lo!-po!er %&S'

()perimental results

*uture !or+


3/48

NCHUCS 3

utline

Overview Scan chain order" does it matter#



*uture !or+


4/48

NCHUCS 4

Digital 'esting

'o detect manufacturing defects

,pply test patterns and o$serve

output responses 'est patterns generated for targeted

fault models


5/48

NCHUCS 5

Scenario for anufacture 'est

TEST VECTORS

MANUFACTURED

CIRCUIT

COMPARATOR

CIRCUIT RESPONSE

PASS/FAILCORRECT

RESPONSES


6/48

NCHUCS 6

Scan 'est .1/

, structural design-for-testa$ilitytechni0ue

Storage elements are not directlyaccessi$le

Scan test provides an easy !ay fortest access

,pply test patterns to circuit under test.CU'/ Read output responses from CU'


7/48

NCHUCS 7

Scan 'est ./

Se0uential circuit **s are neither controlla$le nor o$serva$le

Com$inational 2ogic3rimary&nput

3rimaryutput

**


8/48

NCHUCS 8

Scan 'est .4/

Normal signal path" parallel load

Com$inational 2ogic

3rimary

&nput

3rimary

utput

**


9/48

NCHUCS 9

Scan 'est .5/

&n scan mode" a shift register

Com$inational 2ogic

3rimary

&nput

3rimary

utput

**

Scan in.S&/

Scan out.S/


10/48

NCHUCS 10

Scan 'est .6/

'o ena$le scan test (ach scan cell has t!o inputs

Normal input

Scan input ,ll scan cells are connected into a shift register

.scan chain/

'urn a se0uential test into a com$inational

one ,pply test patterns directly

$serve test results directly


11/48

NCHUCS 11

Scan Chain

Normally constructed !henplacement and routing are done

'he order does not matter *ind out the shortest scan chain order

'raveling salesman pro$lem .'S3/ ,symmetric 'S3 .,'S3/

S& and S of a scan cell are not at thesame location

N3-complete


12/48

NCHUCS 12

utline

vervie!

Scan chain order: does it matter?



*uture !or+


13/48

NCHUCS 13

Scan 'est for Stuc+-at *aults

rder does not matter ,s long as !e can scan in test patterns

and scan out test responses

1 7 1 7

CU'

1 7 1 7 1 7 1 71010 1100


14/48

NCHUCS 14

inimum Wirelength Routing

Use a 'S38,'S3 solver Slo!

Wirelength can $e 17) !ith randomorder


15/48

NCHUCS 15

2o!-3o!er 'esting

, great concern in recent years

Need to reduce signal transitions

'he source of dynamic po!er in CS Usually the dominant factor

Reorder scan chain to reduces!itching activity

1 7 1 71010

1 7 1 71100

3 transitions 1 transition only


16/48

NCHUCS 16

Delay 'esting .1/

Re0uire t!o-pattern tests *irst pattern" initiali9ation Second pattern" launch transition

Delay test !ith simple scan chain %roadside

'he output response of the 1st pattern arecaptured in the scan chain and $ecome the ndpattern

S+e!ed load 'he nd pattern is the result of 1-$it shift of the

1st pattern


17/48

NCHUCS 17

Delay 'est ./

%roadside test (g: ,pply v1;.1717/< v;.7177/

Com$inational 2ogic3rimary&nput 3rimaryutput

**

1010

0100

0100


18/48

NCHUCS 18

Delay 'est .4/

S+e!ed load Not all test pairs possi$le

nnpossi$le -pattern com$inations

nly npossi$le !ith single scan chain

Reorder scan chain to achieve higherfault coverage

1 7 1 71010

1 7 1 71100

0110

NOT POSSIBLE!! 7 1 1 7


19/48

NCHUCS 19

Hold 'ime =iolation

Not enough propagation delay$et!een ad>acent flip-flops in ase0uential circuit Dou$le latching

3ossi$le solution Reorder scan cells to introduce e)tra

delay


20/48

NCHUCS 20

utline

vervie!


Cluster-based reordering forlower-power BIST


*uture !or+


21/48

NCHUCS 21

vervie!

?oal" Reduce %&S' po!er

,pproach

&nclude a smoother to reduce s!itchingactivity in test pattern generator .'3?/

Use scan chain reordering to recover lostfault coverage

Simple reordering algorithm Wirelength should not increase too much


22/48

NCHUCS 22

verall ,rchitecture

Internal scan chain

CUT

ORAPRPG Smoother

TPG

Internal scan chain 1

Internal scan chain 2

Internal scan chain k

.

.

.

.

O

R

A

P

R

P

G

SmootherP

ha

se

shi

ft

er

Smoother

Smoother

.

.

.

.

Single scan chain

multiple scan chain


23/48

NCHUCS 23

Smoother

0/1

1/0

0/0

0/0

1/0

0/0

1/0

.

.

.

Sn/21

S0

0/1 1/1

1/1

1/10/1

Sn1

Sn/2

.

.

.

1/1

0/0

1/0

0/0 1/0

S1

0/1 1/1

S3

0/1

S0S2

0/1

1/0

0/0

0/0 1/0S1

S0

0/0 1/0

S3

S20/0 1/0

0/1 1/1S

S!

1/1

0/1 1/1

S"

S#

0/1 1/1

n-state smoother 5-state .$it/smoother

@-state .4$it/smoother


24/48

NCHUCS 24

, Simple &mplementation of then-state smother

C

$i%i&e'()'n/2

U*'$o+n Co,nter

T

u

d

q

q

C0

in


25/48

NCHUCS 25

(stimation of 3o!er Reduction

3ro$a$ility of signal transition of ann-state smoother

Compute from ar+ov chain model

(stimation of dynamic po!er -$it .5-state / smoother" 184

4-$it .@-state/ smoother" 1817

nn

P 2

2

2

-01.-10.

+

=


26/48

NCHUCS 26

*ault Coverage

0 0 0 0 0 0 0 1 1 1 1 0 0 0 02'(it smoother

3'(it smoother 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1 0 1 0 1 0 1 0 0 1 0 1 1 0 0PRPG

Smoothed patterns are less random ay create repeated patterns and reduce

fault coverage

Re0uired test cu$e"

)))))71))))))))

NO MATCH!

Reorder scan chain"

)))))7)1)))))))

MATCH 2-bit smootr


27/48

NCHUCS 27

Cluster-%ased Scan Chain Reorder

2ayout surface divided into clusters

Reorder limited in single cluster

Sna+e-li+e glo$al routing

Single scan chain ultiple scan chains


28/48

NCHUCS 28

()ample

Routing s16@67 A11 scan cells

1 cluster6A clusters Silicon (nsem$le


29/48

NCHUCS 29

ptimal Cluster Si9e

&s there an optimal cluster si9e#

$servation

2arge clusters--long vertical connection Small clusters--more hori9ontal crossings

Ho! to find optimal cluster si9e *ind an e)pression of total !irelength

'a+e its derivative !ith respect to clustersi9e c


30/48

NCHUCS 30

(stimate Wirelength in a Cluster.1/

'!o types of order Random order

Sorted according to )-cooridnate

sc1

sc2

sc!

sc3

sc

CL1CL2

sc1

sc2

sc3

CL1


31/48

NCHUCS 31

(stimate Wirelength in a Cluster./

Ho! to estimate the distance$et!een t!o cells anhattan distance

Hori9ontal and vertical distances areindependent

,ssuming cells are randomly distri$utedw

00-

h

sc1X1Y1-

sc2X2Y2-


32/48

NCHUCS 32


()pected vertical distance $et!eent!o cells

()pected hori9ontal distance $et!eent!o cells Random order" w84

Sorted order Summation of all hori9ontal distances" w

[ ]3

1122

0 02121

hdydy

h

yyYYEh h

==


33/48

NCHUCS 33


Random order N" B cells< c1" Bclusters

Sorted order

+

+

+= 31321

2 2hw

c

Nh

wl

+

+

+=

c

HW

c

NHW

c 31

3

12

c

W

c

H

c

Nw

h

c

Nhl +

=+

+

=

331

32

12

22


34/48

NCHUCS 34

ptimal Num$er of Clusters .1/

Random order

,ssuming HW< N8c11

Sorted order

,ssuming HW< N8c14

HW

W

c

N

+=

22

H

W

c

N 32 =


35/48

NCHUCS 35

ptimal Num$er of Clusters ./

Reordering algorithm 2arger clusters give $etter results

,lmost no reordering !hen N8c11

Choose sorted order if no special order ispreferred

ptimal cluster si9e

N8c14


36/48

NCHUCS 36

utline

vervie!



!"perimental results

*uture !or+


37/48

NCHUCS 37

()perimental ResultsWire 2ength.1/

-$it smoother

10

100

1000

0.1 1 10 100 1000 10000

A%erae cells *er cl,ster

1irelen0th.m

m

S3" S23! S1320" S10 S3!1" S3!


38/48

NCHUCS 38

()perimental ResultsWire 2ength./

4-$it smoother

10

100

1000

0.1 1 10 100 1000 10000


1irelen0th.mm

S3" S23! S1320" S10 S3!1" S3!


39/48

NCHUCS 39

()perimental Results*aultCoverage .1/

-$it smoother

3

!

#

"

100

0.1 1 10 100 1000 10000


Testefficienc)

.4-

S3" S23! S1320" S10 S3!1" S3!


40/48

NCHUCS 40

()perimental Results*aultCoverage ./

4-$it smoother

"0123!

#"

100

0.1 1 10 100 1000 10000


Testefficienc

).4-

S3" S23! S1320" S10 S3!1" S3!


41/48

NCHUCS 41

ptimal Num$er of Cells perCluster

Circ,it WL mm-'' S5

6cl,ster 6cells/cl,ster 2'(it smoother 3'(it smoother

GS WLmm- Red4- GS WLmm- Red4-

S#!1 2."1 3# 1.0 2 2.3 '!.2! 3 2.! '!.

S"13 2.#" 3# 1.0 ! 2.0 '".3 10 2.0 '".3

S3 3.30 1# 2.1 3 3.# '10.33 3.# '10."

S11# !."! 1# 2.00 2 .0 '#.# " .0 '#.

S1!23 ."0 3# 2.3 1 #.0! '.3 3 #.0! '.#3

S3" 1!." 100 2.1! ! 1." '".#" ! 1."" '".#1

S23! 22.# 100 2.!" 1 23.21 '2.2 23." '!.1

S1320" !.22 2# 2."3 3 !!."! 1.0# # !.! '0.

S10 3.!0 2# 2.3 10 1." 2.# 2 0. !.3

S3!1" 13#.! "# 2. 1 123.3 .# # 12."2 .1

S3! 1". "# 2.! 10 1"".2 .3# " 1".1! .1

S(" Silicon (nsem$le


42/48

NCHUCS 42

'est (fficienct

Circ,it TL Test 5fficienc) 4-

7ar8o%So,rce9IST

:;SR 2'(it smoother 3'(it smoother

S5 O*timal Cl,ster S5 O*timal Cl,ster

S23! "2! .2 .02 3.!# .!" 3.3 2.00

S1320" !0#"" ". .0 2."3 ".! 3.#! "."2

S10 3""#" .31 #.!1 3.!" ".# 0.#2 2."

S3!1" 1! .!2 ".20 !." .# 3. !.!"

S3! 20 .3# ."# .2 .23 0.3 .2

A%erae ' "."0 ".!# 3. ".2! .3 2.#


43/48

NCHUCS 43

Comparison of ,verage 3o!erCirc,it 6scan

cellsTL FC

4-

:;SR

2'(it smoother< 3'(it smoother< :T'RTPGk=3-

FC4-

S5

FC

4-

O*t.

cl,ster

APRed4-

FC4-

S5

FC4-

O*t.

cl,ster

APRed4-

FC4-

APRed4-

S#!1 ! !0# ".!2 !.1 .1 ".!1 ".31 0." .# .#! 3#.

S"13 ! !0# 1.! ". . .1 3."0 3."0 #.3# 3.3! 3".

S3 ! 12 . #.!1 "." .!" !.2# 0.1" !. .#1 ."

S11# 32 !0# .! 2.#3 2."1 #. .!0 "."2 .!0 ." 30.2

S1!23 1 !0# ". .!0 . ".2 ." #.2 .0 ".0 !."

S3" 21! #3# .# ".1 .# .1 0.2# .0 !." ".0 !!.0

S23! 2!" 1310"2 .#" ".1 1.!0 .3" "".! #." .3 1.#3 ."

S1320" "00 !0#"" ".!2 1.2 #.3" #2.#" 2.1" #.2! ".3 ' '

S10 #11 3""#" 3.0# 0.12 !.!3 .21 ".2" .!! !.# ' '

S3!1" 1##! 1! #.#" !.2# .!2 #0."3 2." 3.3 !.3 ' '

S3! 1!#! 20 ."0 1.0 .00 #0." #.1! 1. !.1 ' '

A%erae ' ." 0.3 .11 .## 0. .!# .!! 2. !!."1

*ull scanE " only state vectors are scanned


44/48

NCHUCS 44

3ea+ 3o!er

Capture-cycle po!er is not reduced

Still provide some improvement

Circ,it PPRed4-2'(it smoother 3'(it smoother

S3" 13.31 11.#!

S23! 13." 1#.#

S1320" 12.# 1.#

S10 13.#0 20.23

S3!1" 13." 1.2!

S3! 13.12 1.01

A%erae 13.3" 1".#3


45/48

NCHUCS 45

utline

vervie!




#uture wor$


46/48

NCHUCS 46

Conclusion

Scan chain reorder is very effect todeal !ith 'est po!er

Scan-$ased delay test

*ault coverage in %&S'

Need to consider 3hysical design infromation


47/48

NCHUCS 47

*uture Wor+

*ast reordering algorithm for delaytest

&ntegrate reordering algorithm

0 scan chain reorder

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