Tektronix 7834

Theory of Operation-7834
1195-32
1
I

I
n I
fD
1 N I M

I n
I
l~

I r
TIME-SLOT
PULSE 1
PIN 3
TIME-SLOT
PULSE
2
PIN 13
TIME-SLOT
PULSE 3
PIN 12
TIME-SLOT
PULSE 4
PIN 11
TIME-SLOT
PULSE 5
PIN 10
3- 42
TIME-SLOT
PULSE 6
PIN 9
TIME-SLOT
PULSE 7
PIN 7
TIME-SLOT
PULSE 8
PIN 6
TIME-SLOT
PULSE 9
PIN 5
TIME-SLOT
PULSE 10
PIN 4
L
- .++,++++-+
H
0V
0v
0V
ov
ov
~ov
Also, a Word Trigger pulse is produced by
U3447D when a
Jump Command is received at pin 5 of
U3447B . This condi-
0 v

tion can
occur during any time-slot (see
Row Decoder for
further information on origin of the
Jump Command)
.
U3447A and B are connected as a
bistable flip-flop . The
positive-going Jump Command at
pin 5 of U3447B pro-
duces a LO at pin 4 . This LO is
inverted by U3447A to
produce a HI at pin 1, which allows
pin 6 to be pulled HI
through CR3447 . - The flip-flop
has now been set and re-
mains in this condition until reset,
even though the Jump
Command at pin 5 returns to
its LO level . The HI output
level at pin 1 turns on 03445 to
pull pin 16 of the Time-
Slot Counter LO . This resets the Time-Slot
Counter totime-
slot
1 and holds it there until the Word
Trigger is reset . At
the same time, a HI level is applied
to pin 4 of the Timer
through CR3445 and CR3432 .
This HI level causes the
Timer to operate in the Display-Skip
mode, so a character
is not generated .
0V
oV
0V
Time-Slot
Counter
Time-Slot Counter
U3445 is a sequential switch which
directs the trapezoidal
waveform input at pin 8 to
one
of
its
10 output lines
. These time-slot pulses are
used to interro-
gate the
plug-in units to obtain data for
the Readout Sys-
tem .
The Trigger pulse at pin 15 switches
the Time-Slot
Counter to
the next output line ; the output
signal is se-
quenced consecutively from time-slot 1
through time-slot
10
. Figure 3-33 shows the time relationship of
the time-slot
pulses .
Notice that only one line carries a
time-slot pulse at
any given
time . When time-slot 10 is completed,
a negative-
going
End-of-Word pulse is produced at
pin 2 . The End-of-
Word pulse provides a drive pulse for
the Word Trigger stage
and also
provides an enabling level to
the Display-Skip
Generator
during time-slot 1 only .
Pin
16
is a reset input for the
Time-Slot Counter . When this
pin is held LO, the Time-Slot Counter
resets to time-slot 1 .
The
Time-Slot Counter can be reset in this
manner only
when a
Jump-Command is received by U3447A
and B (see
following
discussion) .
Word
Trigger
The Word Trigger stage is made up of
U3447C and D .
Quiescently, pin 8 of U3447C is
LO as established by the
operating conditions of
U3447A and B . Therefore, the LO
End-of-Word pulse produced
by the Time-Slot Counter
results in a HI level at pin 10
of U3447C . This level is
in-
verted by U3447C to
provide a negative-going
Word Trigger
pulse to the
Channel Counter .
The next Trigger pulse is not
recognized by the Time-Slot
Counter, since U3445 is locked
in time-slot 1 by U3447 .
NOTE :

TEST OSCILLOSCOPE
EXTERNALLY TRIGGERED

However, this -
Trigger pulse resets the Word Trigger stage
FROM TP3450 .
SWEEP RATE UNCALIBRATED .

through C3445 . Pin 1 of U3447A goes LO to enable the
Figure 3-33 . Timer relationship of the time-slot (TS)
pulses pro-

- Time-Slot
Counter and Timer stages for the next time-slot
duced by 03445 .

pulse . Simultaneously,
when U3447A switches output