Tektronix 5440 Instruction Manual page 44

Circuit Description-5440
Th e signals at pin 12, 13, 14, and 16 are pro
d
uced only The next signal to be p roduced is the c hannel switch off
wh en the triangle waveform is on its
n
egative slope an
d
t
he
comman
d
at pin 13 . Th is p ositive-going signal dis-
trapezoidal waveform has reac h e
d
th e lower level . The connects the plug-in signals in the vertical and
h
orizontal
timing sequence of th ese waveforms is very important to
deflection system so that the
p
lug-in units do not control
th e correct o
p
eration of th e readout system (see ex
p
ande
d
t
h e positio n of the crt beam during the rea
d
out d is
p
lay.
waveforms i n F ig . 3-3) . Th e Ζ-Axis blan k at pi n 14 is
T
h
is signal is also connecte
d
to the
d
ecimal point logic
pro
d
uced first. Th is negative-goi ng signal drives 01015 and c h aracter p osition cou nter stage and the format
wh ic h removes th e current in
p
ut for th e interface to t he Ζ- generator stage. T he readout u nblank ing outp ut at p i n 12
Axis Amplifier to blan k th e crt before the dis
p
lay is is produced next . Th is curre nt is con necte
d
to the Ζ-Axis
switched to t h e rea
d
out system . It also pro
d
uces the
Am
p
lifier to unblan k
t
h e crt to the intensity level
d
eter-
strobe pulse th roug h R 1010, 01010 an
d
CR 1013 to sign al mined by RE ADOU T intensity co n trol
R
1000 . However,
ot h er stages with in the rea
d
out system to begi n th e 01018
p
revents the intensity current from reac h ing t h e Ζ-
se q uence necessary topro
d
uceacharacter. T hecollector Axis Am plifier until th e c h aracter scan ram
p
at p in 16
level of 01010 is also connected to c h aracter generator
begins its positive slo pe. T h e c h aracter scan ramp at pin
No . 2, U 1092 th roug h Ο 1010-C R 1010 . This activates
16 starte
d
to go negative as this timi ng se q uence began .
U
1092 during the
q
uiescent period of the strobe p
ulse
The triangular c haracter scan ram
p
runs negatively from
(collector of 01010 negative) and d iverts th e out
p
ut about -2 volts to about-8 .5 volts, t h en returns bac k to the
current of row decoder U1035torow2 .T hepurpose ofthis original level . Th is waveform provides th e scanning signal
configuration is to p rovent the zeros logic and memory
for the c
h
aracter generator stages . Full character sca n
stage U 1060 from storing incorrect d
ata
d
uring the
ad j ustment
R
1006 sets th e do level of t h e c h aracter scan
quiescent
p
eriod of the stobe
p
ulse . Wh en t h e strobe pulse ramp to provi
d
e com
p
lete ch aracters on th e dis p lay.
goes
p
ositive, C R 1010 is reverse biased to
d
isconnect
01010 from U 1092, an
d
allow the row
d
ecoder to operate
in t he normal manner .
Th e timer stage o
p
eratio ns in one of two modes, as
controlle
d
by the dis
p
lay s k i
p
level at
p in 4. T he basic
mode j ust described is α conditio n th at does not occur
unless all te n
c
haracters of eac h wor
d
(80 c haracters total)
(1088)1449-1 ο
are d isplayed on th e crt . Un der ty pical co nditions only α
5ν
20 μS
few characters are dis
p
laye
d
in eac h word . The
d
isplay
0 V
sk i
p
level at p in 4 d etermines th e perio
d
of the timer output
Character Scan
signal . Wh en α ch aracter is to be generate
d
, p i n 4 is L O and
Pin 16
th e circuit o
p
erates as j ust d escribed . However, w h en α
c
h aracter is n ot to be
d
is
p
laye
d
, α Η Ι level is a
p
plied to pi n
4 of U1000 t h roug h CR 1003 from the d isplay sk i
p
generator stage . Th is signal causes the timer to shorten its
period of o peration to about 210 microsecon
d
s . The
5
V
20μS
waveforms i
n F
ig . 3-4 s h ow th e o
p
eratio n of the timer
Z-axis Logic
stage when th e d is
p
lay sk i
p
condition occurs for all
O
FF Command
p
ositions in α word . N otice t h at th ere is no output at pins
P
in 14
12, 13,14, and 16 un
d
er t h is con
d
ition . Th is means t hatthe
crt d is
p
lay is not interrup ted to display characters . Also
0 ν
notice that t he triangle waveform at pin 6
d
oes not go as far
negative and
t
hat th e negative portion of the tra
p
ezoidal
1 ν 20 μ S
waveform at pin 10 is shorter. Com
p
lete details on
Vertical a n
d
o
p
eration of th e dis
p
lay-sk i p generator are give n later.
H
orizontal
C h a nnel
Switch
O
FF
Command
0 V
Pin 13
;Eg
200mV
20 μS
R
eadout
Intensity
~+6 V
P i n 12
NOTE : Test oscilloscope externally trigge red
f
rom ch a nn el
address 4.
F
ig . 3-3. Detail of output at p i ns 12, 13, 14 and 16 of 01000 .
3- 8
READO UT intensity control
R
1000 sets th e i ntensity of
t h e readout dis
p
lay inde
p
en
d
ently of th e I N TEN SITY
control. Th e RE ADOUT i nte nsity control also provi
d
es α
means of turning the rea
d
out system off when α readout
display is not
d
esired . Wh e n R 1000 is turned fully coun-
terclockwise, switch S1000 o
p
ens . The currentto
p in 11 of
01000 is interru pted an
d
, at t h e same time, α positive
voltage is a p
p
lie
d to
p in 4 th roug h R1003 a n d CR 1002 .
This positive voltage switches the stage to th e same
con
d
itio n th at were p resent under t h e
d
is
p
lay-s k ip co n-
ditions . T herefore, the crt
d
is p lay is not interrupted to
present c h aracters . However, time-slot pulses continue to
be generated .