A
Model
o
VLSI
Implemen a ion
o
CNN Image
P ocessing Chips Using Cu en -Mode Techniques
S.
Espejo,
A.
Rod iguez-VBzquez, R. Dominguez-Cas o,
B.
Lina es and J.L. Hue as
Dep . o Analog Ci cui Design. Cen o Nacional dc
Mic oelec 6nica-Uni c sidad
dc Sc illa
Edi icio CICA. Cna ia sn. 41012-Se illa, SPAIN
Phone
#
34
5
46238
1 1.
FAX
#
34
5
4624506.
email: [email p o ec ed]
Abs ac -
A
new Cellula Neu al Ne wo k model
is
p oposed
which allows simple and as e
VLSI
implemen a ion han
p e ious models. Cu en -mode building hlocks a e p esen ed
o he design o
CMOS
image p ep ocessing chips ( ea u e
ex ac ion, noise il e ing, compound componen de ec ion,
e c.) using he cellula neu al ne wo k pa adigm. A ea e alua-
ion o he new model shows a educ ion o abou
50%
as
com-
pa ed
o
he
use
o cu en -mode echniques wi h con en ional
models. Expe imen al measu emen s o CMOS p o o ypes
designed in
a
1.6pm n-well double-me al single-poly echnol-
ogy
a e epo ed.
I.
INTRODUCTION
Cellula Neu al Ne wo ks (CNN) consis o a ays
o
clc-
men a y p ocessing uni s
(cells).
each one connec ed only o
a
se
o
adjacen
cells
(iwighho s).
The educed conncc i i y
allows high cell densi y
in
e ms
o
silicon a ea. and Eicilila cs
CNN
physical design. Fo hc class o
mislo ioiicill~
ii w i(ii
CNNs.
in which all inne cells
ue
iden ical. p og amm;ibilily
can
be
inco po a ed wi hou
a
signi ican ou ing cos .
by
jus
adding a ew global con ol lines. onc pc weigh . CNN
p op-
e ies. and i s applica ion
o
image p ocessing. pa c n
ecogni ion. mo ion de ec ion. e c.. ha e bccn co e ed
in
di -
e en pape s. o ins ance
[
1-91.
This communica ion ocuses
on
CNN
VLSI
implemen a ion. o which li le li e a u c
is
a ailable
[10.11].
Fi s . a new
CNN
ma hema ical modcl
is
p esen ed which exhibi s
some
ad an ages
o
VLSI
implc-
men a ion
as
compa ed o he con en ional model duc
o
Chua
and Yang
[I].
Then. we conside Ihc implemen a ion
o
his
model
in
cu en domain. Since
CNN's
a e basically imcd lo
image p ocessing applica ions. and p ima y ou pu
o
image
senso de iccs (pho o ansis o s
[
121)
is cu cn . his implc-
men a ion s yle is ad an ageous
as
compa ed o p e ious p o-
posals. whe c cell inpu signals a c ol ages. Thc esul s
ob ained show be e a ca. powe and spccd Ligu cs han p c i-
ous CNN implemen a ion echniques.
11.
EXTENDED
RANGE
CNN
MODEL
P e iously epo ed
CNN
IC
dcsign app oachcs ocuscd on
he
use
o
gn,-C
echniques o hc implemcnla ion
o
hc
Chua-Yang's cell ci cui model
[I].
shown
in
Fig.1. whosc
0-7803-1254-6/93$03.00
Q
1993
IEEE
dynamic is gi cn by Ihc ollowing sc
o
nonlinciu s a c-equa-
lions,
VCE
g!D
whe e
N,.(c)
ep esen s hc
cpII
eighho ood.
including cell
I'
i sel .
qD
is hc nc
g id
do i iin.
and hc
cdl
oii pii s
(J~)
a c
ob ained om he
s o e
w iohli~s,
.id,
by hc ollowing nonlin-
ca unc ion.
The coe icicnls
A/
mu/
R;
.
wi h
d
E
N,( ),
can bc a anged
in
wo ma iccs
A'
and
I)'.
callcd hc iw1h ic.k and
wii ol
/m-
plo es
cspccli cly. whilc
il'
is known
;IS
hc
0 l.w
e m. Thc
lime cons an
T
is assumcd in a i;in om ccll o ccll. Fo ans-
lalionally in a ian CNNs. hc o sc c m and
Ihe
en ies
o
A
and
I3
a c
also
ccll-in a ian .
Compula ional p opc ics
o
his modcl cly on i s abili y o
yicld.
o A >l.
Iwo slahlc cquilih ium poin s sepa a ed
by
an
inslahilily cgion. and
in
Ihc possibili y
o
modi ying he s ablc
poin all ac ion cgions hy changing hc ncighbo con ibu-
lions,
d
?
..
.......
......
....
.......
-
-
- -
-
Fig.
1:
Cliua-Yiing
CSN
Ccll
Ci cuil
Modcl
(1
I.
970
This is illus a ed
in
Fig.2. showing he
~(d?/d )
s.
cha -
ac e is ic o he di e en quali a i e si ua ions possible. The
displayed dynamic mu es show ha he a ac ion egion o
he equilib ium poin on he igh (equilib ium poin s
a e
a he
in e sec ion o he cha ac e is ics o he ho izon al axis)
becomes na owe o
I
dec easing; o
/=Il.
his poin
becomes i ual.
A
simila si ua ion happens o he equilib-
ium poin on he le , in case
I
inc eases.
Analog
VLSI
implemen a ion o
(1)
mus handle di e en
a ia ion anges o he s a e and he ou pu a iables.
as
illus-
a ed in Fig.2: while ou pu a iables a e es ic ed o [-1.11
by
(2).
s a e
a iable excu sions
a e
no
cons ained. al hough
i can
be
shown
[
11
ha hey emain bounded by he ollowing
no malized maximum alue,
which. o ypical empla es, anges be ween
5
and 10. Thus,
in
he p e iously epo ed
g,-C
ci cui s
[
10,
111. whe e
all
esis-
i e componen s
in
Fig.1
a e
ealized by di e en ial inpu
ansconduc o s. la gely di e en biasing condi ions and
design equa ions
mus
be conside ed o he ansconduc o s,
hus complica ing he sizing p ocess and yielding non-op i-
mum powe consump ion and a ea igu es.
A
new con inuous ime (CT)
CNN
cell model is p oposed
he e
o
o e come d awbacks
o
(1)
while p ese ing i s com-
pu a ional p ope ies. The cell s a e equa ion o his new
model
is
gi en by.
VC€
ip
whe e
g(.)
is a h ee pieces piecewise linea cha ac e is ics
gi en by.
--NZ(XC+1)
+1
s <-l
-
nz
(XC
-
1)
-
1
.IC
>
1
g
(xC)
=
lim
{
-s
o iie wise
(6)
This model yields wo s able equilib ium poin s sepa a ed
by an ins abili y egion. as (1) does.
Also
as
in
(1).
he a ac-
m
-+
-
Fig.
3:
Dynamic Rou es o he
p oposed
CNN
model:
/,</,cO<13c/,.
ion egion o he s able equilib ia can
bc
modi ied by chang-
ing he
I
pa ame e . This is illus a ed
in
Fig.3. As
a
di e ence
o (1). in he new model all a iables ha e he same a ia ion
ange, wha . when i comes o silicon. is e y appealing
o
educe powe and ccll a ea and o simpli y
hc
design p ocess.
La ge p oduclion yields a e
also
ound
o
ci cui s based on
his new model. specially when dealing
wi h
low ol age ech-
nologies.
111.
CURRENT MODE
BASIC
BUILDING
BLOCKS
The ope a ions equi ed o he implcmen a ion o
(5)
and
(6)
a e:
si mn n io i. weigh ed eplica ion. ionlinen
linu a ioa
and
i i eg o io i.
In
cu en -modc. summa ion is simply
achie ed by ou ing signals o a common node. Weigh ed ep-
lica ion is ob ained by using
i e i
nii ws.
In
MOS
echnol-
ogies. he scaling ac o is con olled by l ansis o sizes. Since
in
cu en mi o s cu en s always low
in
he .same di ec ion,
bias-shi ing is equi ed o allow o he symme ic exis ence-
in e al
o
he a iables. These concepls
a c
illus a ed
in
FigA(a) and
(b).
Sc c al ou pu cu en s
wi h
Ihc same
o
di -
e en scaling ac o s can
be
ob ained by using di e en ou pu
ansis o s.
Nonlinea limilalion is also ob ained using cu en mi o s.
In FigA(b). a sa u a ion nonlinea i y appea s as a esul o he
cu -o o hc inpul Icinsis o . By cascading wo
o
hese s uc-
u es. he nonlinen i y
in
(2)
is
ob ained. as shown
in
Fig5
Finally.
a
cu en -mode lossy in eg a o can
be
easily implc-
men cd by exploi ing eac i e pa asi ic beha io o a cu en
mi o .
as
illus alcd
in
Fig.6. whose small signal beha io is
dcsc ibcd by he ollowing equa ion,
whe e
'5
is gi cn by
'5=CIg,,,,
g,,,
bcing he small signal
ansconduc ance o he ansis o s
in
he cu en mi o . Unde
Fig.
2:
Dynam'ic Rou es o he Chua-Yang
CNN
model:
/,</<Oc ,</,.
Fig.
4:
a)
MOS
cumen mi o :
h)
MOS
cu en mi o wi h hias shi ing.
97
1
Q
..........
$+
li ,
..........
.-IQ
Fig.
5:
Implemen a ion
o
he
nonlinea ope a o /(*)
la ge signal ope a ion, he lossy in eg a o ime cons an
becomes
a
unc ion o he ou pu cu en ( h ough
g,,,).
How-
e e .
i
can
be
shown ha his nonlinca i y does no al e hc
compu a ional p ope ies o cu en -mode CNNs. bu jus p o-
duces sligh changes in he ansien esponse.
Cu en sa u a ion a he lossy in eg a o ou pu can bc
exploi ed
o
he implemen a ion o he nonlinca i y equi cd
in
he new model. gi en by
(6).
No c ha bias cu cn
in
hc
in eg a o
o
Fig.6 de e mines he lowe ex eme o he s a e
a iable ange
(I,
>
-IQ).
The uppe ex eme is de e mined by
he
loading de ice. Thus. by using he same bias cu cn
la
o
his loading de ice, we o ce he in eg a o ou pu cu en o
emain con ined inside he in e al
[-/a.
la].
hus ha ing a
e y simple way o implemen
(6).
No c
also
ha . sincc ou pu
and s a e a iables a e con ined o hc s;imc in e al. he phys-
ical implemen a ion
o
(2)
is no equi ed.
The abo e men ioned building blocks can
also
be
ealized
by enhanced
CMOS
mi o s (scl -biased cascodc. cascodc.
se o-mi o s. e c.), as can be equi ed o educe c o s due
o
ini e
Ea ly ol ages. The esul ing a ea and speed penah-
ions
a c
usually no se e e.
IV.
CELL ARCHITECTURE
Fig.7 shows
a
concep ual diag am
o
a
CNN cell, acco ding
o
ei he
(1)
o
(5).
Weigh ed eplica ion is achie ed
wi h
he
ci cui
in
Fig.4(b). When sign in e sion is equi ed.
an
addi-
ional eplica ion s age is cascaded. Fo he ealiza ion o
(5).
he nonlinea ope a o is implcmen cd
by
p ope ly 1o;iding he
inleg a o block, and hence, he nonlinea opc ao block is no
equi ed.
Fo simplici y,
1/0
ci cui y has no been included
in
hc dia-
g am
in
Fig.7. Ini ial s a e alues
~"(0)
and ex enlid inpu s
14'
can be elec ically se ,
o
op ically ansmi ed using pho oac-
li e de ices
[
121.
Ou pu o each cell can be e alua ed
wilh
hc
help
o
an
addi ional eplica ion b anch. Fu hc I/O conside -
a ions a e needed
o
educe pinagc
o
1;ugc-ncl chips.
DYNAMIC
.
NONI.IM:AK
I"
OPERATOR
OPERATOR
WEIG'lTE
-L
I
SR'
Fig.
7:
Gene ic cu cn -nioclc
CNS
ccll
a chi ec u e
No e ha weigh ed eplica ion is pc o mcd
a
he ou pu
o
each cell. In o he wo ds. cach ccll p oduccs a di e en ou pu .
wi h he equi ed weigh . o each neighbo .
A
each cell.
neighbo con ibu ions
a c
added
a
hc inpu node
as
hey
a e
ccei ed.
In
o de o a oid con usion whcn dcsigning cu cn -
mode
CNNs.
i is con enien
o
wo k wi h ncw empla e
m:i i-
ces. ob aincd in e changing
A;'
by
A,"
and
R,"
by
Bde.
Fig.8(a) shows he comple e cell schcma ic
o
;i
conncc cd
componcn de ec ion
(CCD)
CNN
161.
using
singlc ansis o
mi o s. Fo hc sakc
o
illus a ion. T;ihlc
I
gi cs hc olal ccll
;i ca o di e cn cmpla cs
in
;I
I
.6pm CMOS echnology, co -
esponding o
he
usc o cu cn -mode echniques o he
implemcn alion
o
bo h hc Chu;i-Yang and he ex ended angc
model. Cascodc ansis o s
wi h
Wdpm and
L=.3.2pm
a c
used o he cu cn mi o building blocks. as illus a cd
in
Fig.S(b). Al hough da a
in
T iblc
I
docs no includc hc
a cs
occupied by hc ini ializ;i1ion ci cuil y; app oxima c pixcl-dcn-
si ics : igc om
60
o
160
cclls/mm- (dcpcnding on hc
pa -
licula lemplalc) whcn he p oposcd inodcl is uscd.
V.
EX
IW
I
MENTA
I.
Rlisui
:Is
Expe imen al csul s o
;I
CCD CNN p o o ype, dcsigned
in
a
1.6pm double-mc ;il singlc-poly CMOS echnology, a c
summa izcd hc c. Thc dcsign ac ually includes wo p o o ypes.
cach
wi h
six ccn cclls
in
;I
ow.
Fi s p o olypc
(PI)
co c-
sponds o hc schcm: ic
in
Fig.#(:!) whilc hc second o lc
(P2)
co esponds
lo
Ihc con cn ion; l CNN model by Chua and
Yang. Bo h p o o ypes wc c dcsigned using hc cu cnl-modc
cchniquc desc ibcd : bo c.
Design p occss bcgins by choosing
;I
o i ?
bi s
ii m/
(Iq)
which
in
ou casc
W;IS
2pA.
A
cuimil mi o capable o
d i ing
?la
and
a
IQ
cu cn sou cc mus hcn bc dcsigned.
C:iscodc s uc u cs wc c uscd
in
ou dcsign
o
implcmcn bo h
he cu cni mi o and hc cu cnl sou cc.
All
ansis o s had
Fig.
6:
Lossy
in eg a o .
Fig.
8:
a)
Schcnw ic
id
;I
CSS
ccll
o
CCI):
h)
CilsciXIc
s uclu e.
972
REFERENCES
L.O.
Cua and 1.. Yang: "Cellula Neu al Ne wo ks: Theo y".
lEEE
T o is.
Ci c i s
o id
Sys en s.
Vol.
CAS-35. pp 1257-1272. 1988.
L.O.
Cua and
L.
Yang: "Cellula Neu al Ne wo ks: Applica ions".
/EEE
T o s.
Ci c i s
and
S s cn s.
ol. CAS-35. pp
1273-1290.
1988.
L.O.
Chua and
I.
Roska: "S abili y
o
a
Class
o
Non ecip ocal
Cellula Neu al Ne wo ks".
/EEE
T a s.
Ci c i s
o d
S, s en s.
Vol.
L.O.
Chua and
F'.
Thi an: "An Analy ical Me hod
o
Designing
Simple Cellula Neu al Ne wo ks".
IEEE
7 am.
Ci ei
a id
Sys en s.
J.A.
Nossek e al.: "Cellula Neu al Ne wo ks: Theo y and Ci cui
Design".
/!i .
J.
Ci c i
Tl co
Applica io is.
1992
( o
appea )
T.
Ma sumo o e al.: "CNN Cloning Templa e: Connec ed Componen
De ec o ".
/EEE
l' u is.
Ci c i s
and
Sys cn s.
Vol. CAS-37. pp 633-
635.
1990.
T.
Ma sumo o
e
al.: "CNN Cloning Templa e:
Hole
Fille ".
/EEL
T. Ma sumo o
e
al.: CNN Cloning 'lenipla c: Shadow Dc cc o ".
/.EEL
7' -u s.
Ci c s
u dSys i~nis.
Vol. CAS-37. pp 1070-1073. 1990.
S.
Ma sui and
I.
Okumo o:
"A
Two-Dimensional Segmen a ion-F ee
Laming Recogni ion Sys em hy a Cellula Au onia on A ay using
Eigen ec o s
o
he Second Momen Ma ix".
/E/(-/:
T u aoc io s.
CAS-37. pp
1520-1527.
1990.
Vol.
CAS-38.
pp 1332-1341. 1991.
T~u~Is.
CI c/ /I.
c d
S!,.VIcn . .
Vol.
CAS-37.
pp
635-638.
1990.
Vol. E-74. pp 2132-2440. 1991.
Hole Filling
Noise Fil e ing
TABLE
I
CELL
AREA
FOR
DIFFERFN
TEMPLATES
AND
CNN MODELS
10921 24774
5460 14258
A ea
(pm')
A ea
(pin')
C.C.
De ec o .
1269
1
Shadow De ec o .
16533
Bo de s Ex ac.
1537
1
26291
I
Co ne sEx ac.
I
16381
I
28212
1
a)
b)
Fig. 9: Cell layou s:
a)
p o o ype
PI
:
b)
p o o ype
P?
I1OlJ.M.
CNZ
and I..O. Chua:
"A
CNN Chip o Connec ed Componen
De ec ion".
/EEE
l' a w.
Ci c i s
a id
Sys en s.
Vol.
CAS-38.
pp
812-
817.1991.
11
11K. Halonen
e
ai: "V1,SI lniplcnien a ion
o
a Recon igu ahle Cellula
Neu al Ne wo k Con aining Local Logic".
/!i .
-1.
Ci c i
Theo y
Applica in is.
1992 ( o appea )
I12JA.H.
Sayles
and
J.P.
Uyemu a:
"An
Op oelec onic
CMOS
Memo y
Ci cui o I'a alell Ik cc ion and S o age
o
Op ical Ila a".
EEE
J.
Solid-S a
C' c i .
Vol.
SC-26.
pp
1
110-1
115.
1991.
[
1.31s.
Espejo:
PIi.D.
/~ ssc* o io .
Uni e si y
o
Se ille. Spain.
(In
' og
css.
)
I
I
I
Fig.
10:
Expe imen al nieasu enien s oni p o o ype
PI.
973