Dedicated Mode Switch (Option 21 Only); Main Interface; Input/Output Conditions For Readout Display - Tektronix 7844 Instruction Manual

Readout Display Logic
The Readout Display Logic stage produces vertical and
horizontal lockout pulses (positive-going) to the Readout
System (diagram 1 7). The lockout pulses inhibit the readout
display of the appropriate plug-in unit. Four negative-input
AND gates (U31 91 A, B, C, D) provide lockout pulses for the
R IGHT V ERT, LEFT VERT, B HORIZ, and A HORIZ com­
partments, respectively. Figure 3-3 provides input/output
conditions for the various lockout outputs.
BEAM D I SP LAY E D
V E RTICAL HORI2
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tv
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i
LEFT L E FT A A
A B
LEFT LE FT
l.EFT
L E F T B A
LEFT L E FT
B B
A
LEFT R I GHT A
L E FT R I GHT A
B
LEFT R IGHT B A
B B
LEFT R I GHT
L E F T A A
R I G HT
L E F T A B
R I G HT
B A
RIGHT L E FT
R I GH T LEFT B B
R IG HT
R IG HT A A
R I G HT R IGHT A B
R I G HT B A
R I G HT
R I G H T R I G H T B B
Fig. 3-3. Input/output conditions for Readout Display Logic
stage.
Dedicated Mode Switch (Option 2 1 Only)
The Dedicated Mode Switch circuit includes front-panel
switching and provides the logic for selection of the horizon­
tal compartments that control the horizontal deflection of
beam 1 and beam 2. The LEFT VERT compartment is dedi­
cated to the vertical deflection of beam 1 and the RIGHT
R EV J U N 1 98 1
LOCKOUT AT
P3l l S
LO H I LO H I
LO
LO LO H I
LO LO LO H I
H I LO LO H I
LO H I
LO LO
LO LO LO LO
LO LO LO
LO
LO
H I LO LO
H I LO
LO LO
LO
LO LO LO
LO LO LO LO
H I LO LO
LO
H I
LO H I LO
LO LO H I LO
LO H I
LO LO
H I LO H I
LO
1 6 76·79
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Theory o f Operation-7844/R7844 Service
VERT compartment is dedicated to the vertical deflection of
beam 2 . The Dedicated Mode Switch circuits operate in con­
junction with the Logic circuits (diagram 5) to develop con­
trol signals for use in other circuits within this instrument
and the plug-in units installed. Figure 3-4 shows a detailed
block diagram of the Dedicated Mode Switch. A schematic
of this circuit is shown on diagram 3 at the rear of this
manual.
Horizontal Mode Switching
The Horizontal Mode Switching stage determines the
horizontal display mode, provides plug-in unit alternate
switching information, and
information .
The Horizontal Mode Switching circuits, conSisting pri­
marily of S 1 57 and S 1 59, determine whether the plug-in unit
in the A HORIZ or B HORIZ compartments is to be dis­
played by beam 1 or beam 2. A LO level at P1 34 pins 7, 8, 9,
or 10 indicates the selected mode. Only two pins will be LO
at the same time. The outputs (P1 34 pins 7, 8, 9, and 1 0)
are used in the Horizontal Interface circuits (diagram 1 1 ), Z­
Axis Logic circuits (diagram 5), Auxiliary Z-Axis Logic cir­
cuits (diagram 5), and Auxiliary Y-Axis Switching circuits
(diagram 4).
The Horizontal Mode Switching signals provide plug-in
unit alternate switching information to the Logic circuits (dia­
gram 5). A Hi level on P1 29 pins 4, 5, 7, or 8 determines
which time-base unit (A Horizontal or B Horizontal) alter­
nates the Left Vertical or Right Vertical units. Only two pins
will be HI at a time. The alternate switching information is
coupled to the Left Vertical Alternate Switching stage and
the Right Vertical Alternate Switching stage on the Logic
circuit (diagram 5).
The Horizontal Mode Switching signals are also coupled
to the Readout Display Logic stage (U 1 9 1 ).
Readout Display Logic
The Readout Display Logic stage produces horizontal
mode lockout signals (positive going) to the Readout Sys­
tem (diagram 1 7). The lockout signals inhibit the readout
display of the appropriate plug-in unit. Two negative-input
gates ( U 1 9 1 A, B) provide
lockout
and B HORIZ compartments, respectively. Figure 3-5 pro­
vides input/output conditions for the various lockout
outputs.
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Main Interfacle
The Main Interface block includes circuitry for plug-in in­
terface and interconnections between the plug-in com part-
provides readout display
signals for the A HORIZ
3 -7