Tektronix 7704A User Manual

F ig . 2-17 . I d ealize d wavefo rm s for Vertical Chopp e d B la nk i n g stage .
Cho p Counter
T he C h op Co u nter stage of U 2520 p ro d uces
t
h e
V ertical
C hopping Signal (pin
1),
t h e ( V ertical) C h op Drive (pin
8),
and t h e H orizontal C h opped B lan k ing signal (pin
4) .
Α logic
diagram for
U 2520 is s
h
ow n in
F
ig . 2-18, along wit h
waveforms s h owing t he timing relations h ip
b
etwee
n t h
e
input and o u tp u t signals for t h is stage .
Wh en
t
he H O R IZO N TA L M OD E
switc
h
is set to any
position exce p t C
H O P , p
in 6 remains L
O
a
n
d t
h
e
re
p etition
rate of t he V ertical C h
opping
Signal
at
pin 1 is one- h alf t he
Cloc k rate (see time T
o
to Τ t ) . T h is determines t h e
switc h ing rate between t he left and rig h t vertical compart-
me n ts w he n t h e VER TICA L M OD
E
switc h is set to C H O
P .
At t h e same time, t h e repetition rate of t he
(
V ertical)
C hop Drive at pin 8 is one-fourt h t he Cloc k rate .
T
h is
provides α c hopping signal to d ual-trace vertical units to
provi de switc h ing between t
h
e two c
h
annels .
D u ring t h is
time, t he level at pin 4 will remain
ΗΙ .
Wh en t he H O
R
IZO
N TA L M OD E switc h is set to C H O P ,
t he b asic repetition rate of t
h e
V
ertical C h
op p
ing Signal
a nd t he
(
V ertical) C h op
Drive
is
altere
d .
F
or
example, if t he
H O R IZO N TA L M OD E switc h is
c
h
ange
d at time
Τ , (see
F ig . 2-18), α HI level is applie d to p i n 6 .
O u
tputs at
pins 1
an d 8 will be p r oduce d i n t
h e normal man n er until b ot h
outpu ts are HI . (See time
Τ 2 ; t h is con d ition only occu rs
once
every fift h Cloc k pu lse and only w h en t he H O R I-
ZO N TA L M OD E switc h is set to CHO P .) Wh en both of
t h ese out
p
uts are at th eir HI level, t h e next Cloc k pulse (at
time Τ 3 ) switc h es both out pu ts LO, and at t
h
e same
time,
switc h es t h e H orizontal C
h
oppe d
B lan k i ng o u tp u t to t he
L O level, w
h
e r e it
remains until t he start of t h e next Cloc k
ρυ Ι se .
Circ u it
Desc r iptio n - 7704A Se r vice
T h is change at
time Τ 3 d oes n ot appear at p i n 4
immediately, due to α d elay networ k i n t he circuit . (T
h
e
d elay
is necessary to ma k e t h e
H
orizontal
Ch
oppe
d
B lan k ing coinci de wit
h
t
he V ertical C h o pp e d Blan k i ng
produce d by U 2510A
; compare b ottom two wavefo r ms of
F ig . 2-18 . Also, see V ertical
Ch
opp
e dB la nk ing d escri p tion .)
After t he delay time, t
h
e out p
ut level at p in 4 goes L O to
b lan k t he d isplay .
T he H orizontal C h o pp e d
B lan
k
i ng time must b e longe r
t
h
an
t he V ertical C h oppe d B la nk ing time, si
n ce
it ta k es
more time for t he d isplay to
switc h between h orizo n tal
u nits t h an between
vertical units . D u ri ng t h e time t h at t he
level at pi n
4
is
LO,
t
h e CR T is blan ked and t h e V ertical
C hopping Signal a
nd t he ( V ertical) C h op Drive cannot
ch ange
levels
.
T h e Cloc k p ulse at Τ 3 ch anges only the
H orizontal
Ch
opped
B lan k ing o u tput . T he level on p in
4
goes HI
after t he d elay time to unblan k t h e C
R T .
F or t h e next t h ree Cloc k pulses, t he V ertical C h oppi
ng
Signal output an d ( V ertical) C hop D r
ive
o p
erate
i
n
t he
normal manne r . H owever, at t he fo u rt
h
Cloc k p
u lse (Time
Τ 4 ) both outp uts are again at t h eir HI level . T h e fift h Cloc k
p ulse at Τ 6 switc h es t h e out p ut at p in 1, pi n 8, and
pin 4
(after d elay) to t he L O level to start t
he next cycle . N otice
t h at α H orizo n tal C h o pp ed
B lan
k
ing p ulse is produ ce d at
pin 4 with every fift h Cloc k pulse .
Also notice t h at wit h t h e
H O R IZO N TA L M OD
E
switc
h
set to
C H O P , two com p lete
cycles of t he V ertical C h o pp
ing Signal are produce d wit h
each five Cloc k pulses (repetition
rate, two-fift h s Cloc k
rate) and one complete
cycle
of
t h e ( V ertical) C h op D r ive
for every five Cloc k
pulses (one-fift h Cloc k rate) . N otice
th at t h e large s h a ded area p
roduced b y t h e H orizontal
C ho pp e d B lan k i ng
pulse (see F ig . 2-18) is not part of t h e
d is p lay time
(C RT d isplay blan ke d ) . H owever, a bo
u
t t
h e
same
time segment is d isplaye d from t he vertical
signal
source wit h or with out H orizontal C
h
op pe
d B la nk i n g, du e
to t h e change in re p etition rate w
h en in t he CH O P
h orizontal mode .
T he V ertical Cho pp i ng Signal at pi n 1 of U 2520 is
connected to t he V ertical
M
ode
L
ogic
stage (see followi ng
d escriptio n ) t
h roug h L 2519- R 2519 . Th is signal is Η 1 w h en
t h e rig
h
t
vertical un it is to b e dis p laye d and L Ow hen t h e
left
vertical unit is to be dis p layed . T h e ( V ertical) C h op
Drive
at
pin 8 is connected to t h e plug-in un its in t h e
vertical
compartments t h roug h L 2528- R 2528 via t h e M ain
I
n terface boar
d . Wh en t h is signal is HI, C h annel 2 of t h e
p lug-in units can be d isplaye d ; w h en t h is level is
L O,
C h annel 1 is d isplayed . T h e H orizo n tal C
h
op p ed
B
la
nk ing
signal at pin 4 is connected t h roug h LR 2523 to t h
e
H
orizontal
B i n
a
r y stage U 2530 and to t h e Ζ -Axis L ogic
stage
U 2573by
way
of C R 2524 . Wh en t h is signal is
HI, the
C RT is un b lan ked to dis p lay t h e selecte d
sig n
al
. Wh en it is
LO,
t
he C RT is b lan ked to allow switc
h ing
b
etween t he
h orizontal un its .
2- 23

Tektronix 7704A Specifications

General

Brand	Tektronix
Model	7704A
Category	Test Equipment
Language	English