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F
ig
ur
e 4-4. 10 5/
Η
z
L
ea
d
i
n
g Zero
B
la
nk
i
n
g
F
unction
Mo d el 5383Α
Th eory of O per atio n
DIS PL AY DIGIT
S5
DS1
D
uri n g scan time S7, t h e RB latch is agai n
p
r eset, dr iving t h e o u tpu t of
N
A N D GATE U 20
low .
As α
r
esu lt, t he RB I gate o u tp ut is fo r ced
h
ig h ;
d
efeati n g t he RB I sig n al a nd
allowi n g t h e un it's
H
z ze r o
d
igit, t h e
d
ecimal
p
oi nt, a nd
t
h e 0 .1
H
z ze ro
d
igit to
b
e
d
is p lay (i .e .,
0 .
0
).
S4
DS2
CO N DITIO NS :
ΝΟ INPUT SIG NA L
GAT E ΤΙΜΕ = 10s/Hz
SCAN TIME
s3
S2
I
S1
s
DS3
DS4
DS5
DS6
S9
DS7
S7 , Ι S6
DS9
D
urin g scan time 57,
R
i p ple
B
lank i ng (RB)
L
atc h A1 U 23 is p reset .
P
i n 5 goes
h
ig h ;
drivi n g t h e o u tput of e nabled N AN D GAT E A1 U 20 low . Th e low o u tpu t of
U
20 fo r ces
t h e
R
ipp le
B
lan k i ng I npu t ( RB I) Gate outp ut
h
ig h . Th e
d
isplay digits a r e not eval uate d
a
nd no bla nk ing occurs at this time .
,
T h e low S5 signal fo rces
N
A N D GAT E A1 U20
h
ig h .
T h is
h
igh dr ives enabled RB I gate
U
24 low, allowi n g the
d
is play
d
igits to
b
e eval u ate d . Ze ro is se n se d , ca u si ng t h e most
sig n ifica n t digit to
b
e bla nk ed dur in g S5 a nd
t
h e
R
i pple
B
la nk ing O u tput ( RB O) to
go low .
L
ow RBO clea rs t he RB latch . T he
r
esu lti n g low o utp u t
k
eep s
N
A N D GAT E U20-8
h
ig h ;
w h ich in
t
urn k eeps t h e RB I signal active (low) .
Si n ce th e re is no i npu t signal to th e
coun te r, eac h digit eval uate d is ze ro, causing RBO to remain low .
(CA NT
4-7
FRE Q UEN CY
V
A LUE
10'τ
MHz
UN IT'S
MHz
100' τ
kHz
10' τ
kHz
UN IT'S
kHz
100's
Hz
10's
HZ
'DEAD'
'TIME'
UN IT'S
Hz
0 .1
ι
SIGNIFICANT
DEC.
ί
Ι
( MOST
DIGIT)
POINT
ι
SIG NI F
Ι
DIGIT)
Ι
ι
RB
K
D
L
ATC
H
ι
'
Α1 U 23-5
Ί
Ι ~~
ι
10τ
D
EFEAT
ι
( N A N D)
-
GAT
E
Α1
U
20-8
Ι
Ι
RB I
Ι
ι
Al U24-6
(ι, Ι1.Ι1
ι
ι ΙΙ , Ι~ι
Ι1 ~Γ 1 Ιι. ΙΙ,
~ Ι
R
BO
Ι
Α2υ 1-4
ιΙι,~1Ι, Ιι, ΙΙ ~~ Ιι . Ιι , Ιι , ,
. .
.
.
~Ι~Ι,Ιι,ι~
h
Ιι ~1~1~Ι1~ ι~
h
Ι
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