Tektronix 7834 - Page 76

Theory of Operation--7834
ALT OR CHOP
MODE (HORIZ)
AND NOT
DE-
LAYED MODE
MAIN FRAME
CHANNEL
SWITCH SIGNAL
(DISPLAY
B)
VERTICAL
ALTERNATE
COMMAND
(1195-12) 1988-37
Figure 3-12 . Input and output pins for Vertical Binary IC (U4368) .
Pin 4 HI-HORIZONTAL MODE switch set to ALT or
CHOP with nondelayed sweep .
Pin 7 HI-A
sweep is to be displayed (Display
B LO) .
Pin
10 LO-HORIZONTAL MODE switch set to any posi-
tion except A or B .
The input conditions required to provide a LO output level
to display the LEFT VERT unit at the B-sweep rate are :
3- 20
Pin 4 HI-HORIZONTAL MODE switch set
to
ALT or
CHOP with nondelayed sweep
.
Pin 7 LO-B sweep is
to
be displayed (Display B HI) .
Pin 10 LO-HORIZONTAL MODE switch set to any
position except A or B .
3 . ALT OR CHOP MODE (HORIZ)-DELAYED . If the A
time-base unit is set to the delayed mode when the HORI-
ZONTAL MODE switch is set to either ALT or CHOP, the
operation of the stage is changed from that discussed above .
Now, the Vertical Alternate Command switches between
the
HI
and LO states at a rate that is one-half the repetition
rate of the Display B signal . The resultant crt display in the
ALT position of the VERTICAL MODE switch allows the
RIGHT VERT unit to be displayed first against the A sweep
(delaying) and then against the B sweep (delayed)
. Then
the
display switches to the LEFT VERT unit and is displayed
consecutively against the A and B sweeps in the same
manner . The input conditions for this mode of operation
are :
Pin 4 LO-A time-base unit set for delayed operation
.
Pin
8
HI
or LO-Vertical Alternate command changes
state at
HI
to LO transition of Display B .
Pin 10 LO-HORIZONTAL MODE
switch set to
any
posi-
tion except A or B .
A logic diagram of the Vertical Binary stage is shown in
Figure 3-13A . Several logic functions in this stage are per-
formed by logic devices made up of discrete components .
The components that make up these logic devices are iden-
tified on the logic diagram . An input/output table
for the
Vertical Binary stage is given in Figure 3-13B
.
Plug-In Binary
The Plug-In Binary stage produces the Alternate
Drive sig-
nal to alternate dual-trace units . Figure 3-14 identifies the
function of the input pins for the Plug-In Binary IC, U4412 .
This stage uses the same type of integrated
circuit
as
the
Horizontal Binary and Vertical
Binary stages .
When the Alternate Drive level is H I and the plug-in unit is
set for alternate operation, Channel 2 of the dual-trace unit
is displayed . When it is LO, Channel 1 is displayed .
The
repetition rate of the Alternate Drive signal is determined
by the setting of the VERTICAL MODE switch
. For all
positions of the VERTICAL MODE switch except
ALT, the
Alternate Drive level is the same as the Vertical
Alternate
Command from the Vertical Binary stage . Since
the Verti-
cal Alternate Command is derived directly from
the Display
B signal, the two channels of a
dual-trace vertical unit are
allowed
to be
slaved
to
the time-base units (nondelayed,
dual-sweep
horizontal
modes only) in the same manner as
previously described for independent-pairs
operation be-
tween the vertical and
time-base units . The resultant crt
presentation (when
the
dual-trace unit is set for alternate
operation) displays the Channel 1 trace at the sweep rate of
the B time-base unit and the Channel 2 trace at the sweep
rate
of
the A time-base unit .
The Alternate Drive switches from HI to LO as the Display
B signal (from the Horizontal Binary stage) switches from
LO
to
H I, and vice versa .
When the VERTICAL MODE switch is set to ALT, the
Vertical Alternate Command from the Vertical Binary stage
switches the vertical display between the two vertical
units
.
However, if either of the vertical plug-in units are
dual-trace
units, they can be operated in the alternate mode also . To
provide
a switching
command
to
these units, the Plug-In
Binary stage produces an output signal with a repetition
rate that is one-half the repetition rate of the Vertical
Alternate Command . The sequence of operation, when two
dual-trace vertical units are installed in the vertical plug-in
compartments and they are both set for alternate operation,
is as follows (VERTICAL MODE and HORIZONTAL
MODE switches set to ALT)
:

1 .
Channel
1 of
LEFT VERT
unit
at sweep rate of B time-base unit,
2 . Channel 1
of
RIGHT VERT unit at sweep rate of A time-base unit,
3 . Channel 2 of LEFT VERT unit at sweep rate of B time-
base unit,
4 .
Channel 2 of RIGHT VERT unit at sweep rate
of A time-base unit . Notice that under these conditions,
both channels of the LEFT VERT unit are displayed at the