Tektronix 7623, Instruction Manual

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Circuit Description— 7623/R7623 Service
current from the Decimal Point Logic and Character
Position stage is added to the X (horizontal) input signal to
space the characters horizontally on the CRT (see previous
discussion). The Ready signal at pin 13 activates this stage
when a character is to be displayed on the CRT.
Fig. 3 -36. Readout word relating 10 possible character locations to
the decimal-point instructions that can be encoded and the resulting
display.
TABLE 3-4
Channel Address Code
Pin 11
U2250
Pin 8
U2250
Pin 9
U2250
Channel
Displayed
HI
HI
LO
Channel 1
Left Vertical
HI HI
HI Channel 2
Left Vertical
HI LO
LO Channel 1
Right Vertical
HI LO
HI Channel 2
Right Vertical
LO HI LO
Channel 1
Horizontal
LO HI
HI Channel 2
Horizontal
of the Format Generator through R2280 raises the decimal
point so it appears between the displayed characters.
When decimal-point data is encoded, the CRT is un­
blanked so a readout display is presented. However, since
row 7 does not activate any of the five Character
Generators, the CRT beam is not deflected but instead
remains in a fixed position to display a decimal point
between the characters along the bottom line of the
readout word. After the decimal point is produced in the
addressed location, the CRT beam returns to the location
indicated by the Character Position Counter to produce the
remainder of the display.
Format Generator
The X- and V-deflection signals produced by the
Character Generator stage, are connected to pins 2 and 7
respectively of Format Generator U2284. The Channel
Address No. 2 code from the Channel Counter is also
connected to pins 1, 8, and 15 of this stage. The Channel
Address No. 2 code directs the Format Generator to add
current to the X and Y signals to deflect the CRT beam to
the area of the CRT which is associated.with the plug-in
channel that originated the information (see Fig. 3-24). The
Channel Address Code and the resultant word positions are
shown in Table 3-4. In addition, the character position
Y-Output Amplifiers
The Y-output signal at pin 6 of U2284 is connected to
the Y-Output Amplifier Q2287-Q2299. This stage provides
a low impedance load for the Format Generator while
providing isolation between the Readout System and the
Vertical Amplifier. Vertical Separation adjustment R2291
changes the gain of this stage to control the vertical
separation between the readout words displayed at the top
and bottom of the graticule area.
X-Output Amplifier
The X-Output Amplifier Q2286-Q2296 operates simi­
larly to the Y-Output Amplifier to provide the horizontal
deflection from the readout signal available at pin 4 of
U2284. The gain of this stage is fixed by the values of the
resistors in the circuit.
Display Sequence
Fig. 3-37 shows a flow chart for the Readout System.
This chart illustrates the sequence of events which occurs in
the Readout System each time a character is generated and
displayed on the CRT.
3-47