Tektronix 7704A User Manual

time-m u lti p lexed out
pu
t
at
p i n
7, w
h ic h i n cl u
d es
t
h
e
information fr om
all
of t he inp u t ch a nn els . E ight of t he
n ine in p uts to eac h stage origi n ate in t h e p lug-i n u nits ; t he
nint h input co
m
es fr o
m
α s p ecial d ata-e n co d ing n etwor k
com p
ose d of resistors
R
2058 t
h
roug
h R
2069 an d
R
2070
t hr oug
h R
2079 (see Ze
r
os L ogic and
M
emo
r
y d escri p tion
fo r fu rt
h
er infor
m
atio
n
on
n i n
t
h c h
ann el) .
In a d d itio
n
to
t h e encodi ng d ata i npu ts from t h e p lug-in
u n its, i n pu ts are provide d to the Column Data Switch from
t h e VER TICA L M OD E an d H O R IZO N TA L M OD E
switc h es to in h ibit t he r ea d out fo r any p lug-in un it(s) n ot
selecte
d for d is p lay . Wh
en
α p
lug-i n un
it is selecte d , t h e
respective mo d e
i n pu
t
is
HI
to forwar d b ias t he asso-
ciated dio d es ; C
R
2031-C
R 2033, CR 2035-C R 2037, C R 2041-
C
R
2043, or
CR
2045-C
R 2047 . T h e forward- b iase d d io d es
ca
u
se t
h e ch annel switc h es to b ypass t h e enco d e d
d ata from t he o pp osite c h annel . However, si n ce it may be
desire d to d isplay i n formatio
n from special-pu rp ose plug-in
un its (even t
h
o
u g h
t
hey
do
not pr o d u ce α n o r mal
wavefor m d is p lay on t he CR T), α feature is p rovide
d to
over-ri de t he
mo
d e in h ibit
.
T h
is is d one b y app lyi
ng
α L
O
to t he associate d F
o
r ce R
eadout
i npu
t .
T h
e
L
O level diverts
t he HI mode-i nh i b it cu rrent
an
d
allows t
he
d ata from t
h
is
p l u g-in unit to reac h t he Colu mn Data Switch , even
t
h
o ug
h
it
h
as not been selected for d is p lay by the mo d e switc h
es .
T h
e out pu ts of U 2070 an d U 2030 a r e conn ected to t he
rest of t h e Rea dout System t h ro u g h Q2070 and Q2030,
respectively an d t h roug h t h e M ain Inte r co nn ect . Q2070
an
d
02030 are no rm ally fo r war d b iase d by t he positive
voltage level esta b lis he d at t h eir b ases b y d ivi d er R2051-
C R 2051- R 2053 . T h e Plug-in R ea do u t Disa b le level
f r
om t he M ai n
I
n terconnect goes L O to reve r se- b ias
C R
2051-Q2030-Q2070 .
T h
is d isco nn ects U 2030 an d
U 2070 fr
om t
he
Reado
u
t
System
to allow t he M ain
Interco nn ect to provi d e time-m u lti p lexed
a
n
alog voltages
for t he rea d out d is p
lay .
Row M atc h ad ju stment R3422 sets t h e gai n of t he Row
Data Switc h
to
matc h t he gai n
of t
h
e Row Deco d er for
correct ou t pu t . Colu m n M atc h
a
dj ustme n t R3407 p erforms
t he same f un ction for the Colu mn Data Switch stage .
Display-S k i p
Ge n e
r
ato r
T
he Display-S k ip Gene r ato r is made up of Q3406,
Q3411, Q3414, an d Q3416 . T h is stage mo n itors the
ti
m e-m u
lti p
lexe
d col
um n
d ata at t
h
e o u t p ut of t
h
e Col u m n
Data Switch du ring each time-slot
to
d etermine if
t
he
informatio n at t h is p oi n t is vali d d ata t h
at
s h oul d
result in a
CR T d isplay . Quiesce n tly, t h ere is
a
b out100 microampe r es
of c
u r
r en t flowing t
h
roug
h R
3407 from Q3419 an d t
h
e
Ze r
os L ogic an d
M
emo r y stage . (The p ur p ose of t
h
is
q uiescent
c
u r
r ent
will
b
e
d
isc u
sse d in connection wit
h
t
he
Zeros L
ogic a
n
d
M
emory stage
.) T h is cu rre n t b iases
Q3406A so t h
at
its base is about 0 .2 volt more p ositive
Colu m n and R ow Deco d e r s
Ci r c u it Descri p tio n
-
7704A
Service
t h a n t he b ase of Q3406 Β in t he a b se n ce of col u m n d ata .
T
he r efore, si n ce Q3406A and 03406 Β are conn ecte d as α
compa r ato r , Q3406
Α
will remain on u nless its b ase is p ulle d
more negative t
h
an t
h
e b ase of Q3406
Β .
T h
e analog d ata o
u
t p ut
f
r om t
h
e Colum
n
Data Switc
h
pr
o
du ces
α 0 .5-volt (a ppr
oximately) ch
a
nge
fo r eac
h
un it of
col u m n cu rr e n t t h at h as b ee n enco d e d b y t h e pl u g-in un
it .
W h enever any i nformation a pp ears at t he outpu t of t he
Colu
m
n Data Switc h , the b ase of Q3406A is p ulle d more
negative t han t h e b ase of Q3406 Β , r esulting in α n egative
( L O) Dis p lay-S k i p outpu t to t he Ti m er stage th ro u gh
Q3416 . Recall
t
h
at α
L O
was
n
ecessary at t h e s k ip in pu tof
t h e Timer so it cou l d p e r form t h e com p lete
se
quen ce
n ecessa r y to dis p lay α c h aracter .
Q3411-Q3414
also p rovide Display-S k i p actio n .
T
h e
End -of- W o rd level connected to t h eir emitters
is
L O
only
d u ri ng time-slot 1 . T h is means t hey are e n ab le d
only
du ri n g
t h is time-slot . Th ese tra n sistors allow t he Zeros L
ogic a
n
d
M emory stage to gene r ate α Dis p lay-S k i p signal
d
u r ing
time-slot 1 w
h
e n i nformation t h at is n ot to be d is p laye d
on
t
he
C
R T h
as b een sto r e d i n memory (f u rt h e r informatio n is
give n u nder
Zeros
L
ogic an d M emory d escri p tio n
) .
T he Col u m n Deco d e r U 3418
an
d R
ow
Deco
d er U 3429
se n se t h e magnit ud e
of
t he
analog voltages at t h ei r inp u ts
(p i n 10) a nd p
ro
duce
α
b ina r y
o
u
t pu t on one of ten li n es
co
rr es p
o
n
di
ng
to
t he
column o
r row
d ata
e n
co d ed by t h e
p lug-in u nit . T h ese
out pu ts p
rovi
de t
h
e Col u m n Digital
Data an dR ow Digital Data, w h ic h
is
u
se dby t he C
h
a r acter
Ge ne r ator stages to select t he d esire d c h
aracter
for
d is p lay
on t h e CR T . T h e col u mn a nd row d ata is also u se d t hrough -
o
u
t t he Rea d o u t System to pe r fo r m ot h er functio n s .
T
h e input curre n t at pin 9 of t h e Col um n Deco
d e r stage
is steered to only one of t he te n Colu m n Digital
Data
ou t pu ts . T he size
of t
he
d is p layed ch aracte r is d ete r mi n e d
by the val u e of R3418 . Wh en
α
Dis
p lay-S k i p signal is
p rese n
t (collector of Q3416 HI), p i n 9 is pulle d
HI t
hr
o
ugh
C R 3416 . T h
is en su r es t h at no c urr ent is co nn ecte d to t h e
C ha r acter Gene r
ator stage und e r t h is cond ition . N otice t h e
cor r es pon d i ng i np ut
on t
h
e Row Decode r . T h is in pu t is
co nn ecte d
to g
r ound
and ca
u
ses only one of t he te n r ow
ou tputs to sat u rate to ground .
T h e n
etwork at the i np ut of t h e Row Decoder, m a d e up
of
03427
and its associate d compo n en ts, is α Row-14
d etecto r w h ic h p ro du ces the Ju m p Comman d . T h is r ow
cu rr ent is e n cod e db y special-p urpose p lug-i n s to cause
all
or p art of α wor d to be j um p ed . W h enever r ow 14 (t h i r tee n
u n its of row c urr ent, 1 .3 milliam p e r es) is encode d , t h e b ase
of Q3427 is pu lle d n egative enoug h so t h at t h is tra n sistor is
reverse
b iase d to pr oduce α Η Ι Ju mp Com m and ou t p ut at
2- 5 1

Tektronix 7704A Specifications

General

Brand	Tektronix
Model	7704A
Category	Test Equipment
Language	English