Tektronix 7704A User Manual

F inally, memory C is
interrogate d during time-slot 8 to
o b tain information on
w h et h er t he p refix s h oul d be
ch ange d , or left at t
h e value t hat was enco de d . If data
h
as
b een enco d ed t
h
at
calls for α s h ift i n p refix, α
negative-
going output
level is produced at p in 7 . T h is negative level
s u btracts one unit of
column cu rrent from t h e data at t h e
in p ut to t he Column
Decod er . N otice on t he C h aracter
Selection M atrix of
F ig . 2-33 t h at w hen row4 is p ro-
gramme d , α reduction of
one column results in α one-
column s h ift of t
h e prefix . For example, with t h e 100 μ
V
p rogram s
h own in F ig . 2-40, if t h e d ata receive d from t
he
plug-in calle d
for α s h ift in p refix, t h e C R T readout would
be ch ange d to 1
m V (zeros d elete d by program ;
see
E nco d ing t he Data) .
T h e 100 microamperes of q uiescent
current
t
h roug h
R 3407 provid e d b y 03419 (see
Disp lay-S k ip Generator)
allows t h e prefix to
b e s h ifted from m (100 microamperes
column
current, column 1) to no p refix (zero
column
current, column zero) so only t he unit of
measurement
enco d ed d uring time-slot 9 is d isplaye d .
N
otice t
h
at
re
d
ucing t he prefix p rogram from column 1 to
column 0
programs t h e Rea d out System to not d is p lay α
ch aracter at
t h is rea d out location .
Α furt h
er feature
of
t he Zeros Logic an d M emory is t
h
e
Identify
f unction . If 10 units of column current
are
enco d e d b y t
he plug-in unit along wit h row 3 during
time-slot 1, t
he Zeros L ogic an d M emory produces α
negative-going output
pulse at pin 1 to switc h t he Column
Data Switc h a
n
d
Row Data Switc h to t h e nint h c hannel .
T hen, time-slot pulses
2 t h roug h 9 enco d e an output
current t h roug
h resistors R2058-132069 for column data
an d R2070-
R2079 for row d ata . T h is p rovi d es t he currents
necessary to d is p lay t he word ID EN TI
F
Y in t he wor d
p
osition allotted to t he channel t hat originate d t h e I d entify
comman d . After completion of t h is word, t h e Column Data
Switc
h
an d
Row
Data
Switc h continue with t he next wor d
i n t
h
e se q
u
ence
.
T he Wor d Trigger signal from the Word Trigger stage is
connecte d to pin 9 of U 3401 t h roug h C3401 . At t he
e
nd of
each wor d of rea d out information, t h is p ulse goes L O .
T
h is
erases t he four memories in t he Zeros
L
ogic an d
M
emory in
prep
aration for t
h e
data to be
received from
t
he next
channel .
C
h
a
r acter Generators
T
h e C h aracter Generator stage co n sists of five similar
integrate d circuits ( U 3461 t
h
roug
h
U 3469), w
h ic h generate
t he Χ ( h orizontal) an d
Υ
(vertical) outputs at p ins 16 an d
1, res p ectively, to p ro d
uce
t h
e c
h
aracter
d isplay on t h
e
CR T . E ac h integrated circuit can pro d uce 10 in d ivi d ual
ch aracters . U 3461 (designate d "
Nu
merals") can
p roduce
t h e numerals 0 t hrough 9 s h own in row 1 of t he C h aracter
Selection M atrix ( F ig . 2-33) . U 3463 can p roduce t
h
e
REV .
JUL
Y 1974
Ci r cu it Descri p tio n - 7704A Service
symbols s h own i n row 2 of t h e Ch aracter Selection M atrix
and U3465 pro duces t he p refixes an d some letters,
use d
as
p refixes, s h own
in row 4 . U 3467 and U3469 pro d uce t he
remaining letters s h own in rows 5 and 6 of t he C h aracter
Selection
M atrix .
All
of
t h e C h aracter Generator stages receive t
h
e
Column
Digital Data from t h e Column Decod er U3418
in parallel .
H owever, only one of t he C h aracter
Generators receives
row data at α p articular time and only t
h e stage receiving
t h is row data is activated .
F
or
example, if column 2 is
enco ded , t he five C h aracter Generators are
enabled so t h at
eit h er
α
1,<,μ , V, or an Ν can be p ro d
uce d . If row 4 h as
been enco d ed at t h e same time, only t
he P refix C h aracter
Generator U 3465 will pro d uce an out p ut to result in
α
" μ
"
being
d is p
laye d . T h e activated C h aracter Generator p ro-
vi des
current outputs for t h e
F
ormat Generator to pro
d u ce
t
he selected character on t he C
RT .
In α
similar manner, any
of
th e ch aracters s h own in t h e C h
aracter Selection M atrix
can be
d isplaye d by correct a dd ressing of
t h e row and
column .
Decimal P oi n t L ogic and C haracte r
P osition Cou n ter
Decimal P oint L ogic an d C
haracter P osition Counter
U 3470 performs two
functions . T he first function is to a dd
α staircase current to
t h e Χ
(
h orizontal) signal to space t he
ch aracters
h orizontally on t h e CR T . After eac
h
c
h
aracter
is
generate
d ,
t
he negative-going e dge of t h e Ready
signal at
pin 5 advances t he C h aracter
P
osition
Counter . T h is
p
ro
duces α current ste p out put at p
in 3 w h ic h , w hen a d ded
to t h e Χ signal, causes t
he next ch aracter to be d is p laye d
one ch aracter s p
ace to t he rig h t . T h is stage can also be
a d vanced w
hen
α
Sp ace instruction is encoded so α space
is
left between t
he displaye d c h aracters on t he CRT .
Row
10
information from t h e
Row Deco d er is connecte d to p in
4
of U3470 . Wh en row 10
and column 0 are encode d , t
h e
out p ut of t h is stage a
d vances one step to move t
he next
ch aracter anot
h er s pace to t he rig h t . H owever,
un d er th is
con d itio
n ,
no
d isplay is pro d ucedon t
he CR T during t h is
time-slot, since t h e C h aracter Generators
are not activate d .
Time-slot pulses 1, 2, an d 3 are also connecte d to p in 4
of U 3470 t h roug h VR 3470, VR 3471, an d VR 3472 res p ec-
tively and R3470- R3473 . T h is configuration ad d s α space
to t he displayed wor d during time-slots 1, 2, and
3 even if
information is not encoded
for
display d
uring t hese
time-slots .
Wit h this feature, t he information d is p laye d
d uri ng
time-slot 4 (scaling data) always starts in t he fourth
c h aracter position w h et h
er
d ata h
as
been d is p
layed in
t
he
previous time-slots or not .
T h
erefore, t
h
e
resultant CR T
d isplay does not s h ift p osition as
normal-invert
or cal-
υηεαΙ
information is enco d ed .
T
h e Word
Trigger p ulse connecte d
to pin 8 resets t h e C h aracter
P
osition Co
unter to t h e first
ch aracter position at t h e en d of
each word .
2- 53

Tektronix 7704A Specifications

General

Brand	Tektronix
Model	7704A
Category	Test Equipment
Language	English