Logic Polarity; Input/Output Tables; Non Digital Devices; Block Diagram - Tektronix 7623A Instruction Manual

Theory of Operation—7623A/R7623A Service
NOTE
Logic symbols used on the diagrams depict the logic function and may
differ from the manufacturer's data.
LOGIC POLARITY
All logic functions are described using the positive logic. Positive logic is a system of notation where
the more positive of two levels (HI) is called the true or 1-state; the more negative level (LO) is called the
false or O-state. The HI-LO method of notation is used in this logic description. The specific voltages which
constitute a H] or LO state vary between individual devices.
INPUT/OUTPUT TABLES
Input/output (truth) tables are used in conjunction with the logic diagrams to show the input combi-
nations which are of importance to a particular function, along with the resultant output conditions. This
table may be given either for an individual device or for a complete logic stage. For examples of input/out-
put tables for individual devices, see Table 3-1.
NON-DIGITAL DEVICES
Not all of the integrated circuits in this instrument are digital logic devices. The function of non-
digital devices will be described individually.
BLOCK DIAGRAM
All major circuits and basic interconnections of the 7623A are represented in the block diagram, Figure
3-1. The numbered diamond in each block refers to the respective schematic diagram for that circuit, located
at the rear of this manual.
The Main Interface, block 1, provides the interconnections between the plug-in compartments and the
various circuits and functions of the instrument.
Signals from both vertical plug-in compartments are applied to the Vertical Interface circuit. This
circuit determines whether the signal from the left or right plug-in unit is displayed. The selected vertical
signal is then amplified by the Vertical Amplifier circuit to drive the vertical deflection plates of the crt.
The Vertical Amplifier also accepts the Y-Readout signal from the Readout System to producethe verti-
cal portion of the alpha-numeric readout display.
Signals from the horizontal plug-in compartment are applied to the Horizontal Amplifier circuit where
they are amplified to provide horizonta! deflection of the crt electron beam. The Horizontal Amplifier
circuit also accepts the X-Readout signal from the Readout System to produce the horizontal portion of
the readout display.
3-5