Tektronix 5441 Instruction Manual page 55

Theory of Operation-54411~15441
the displayed characters on the crt. Row 10 information
from the row decoder is connected to pin 4 of U1080
through R1083. When row 10 and column 0 is encoded, the
output of this stage advances one step to move the next
character another space to the right. However, under this
condition, no display is produced on the crt during this time-
slot, since the character generators are not activated.
Time-slot pulses 1, 2, and 3 are also connected to pin 4
of U1080 through VR1080, VR1081, and VR1082, respec-
tively, and R1088, R1082. This configuration adds a space
to the displayed word during time-slots 1, 2, and 3 even if
information is not encoded for display during these time-
slots. With this feature, the information that is displayed dur-
ing time-slot 4 (1-2-5 data) always starts in the fourth
character position whether data has been displayed in the
previous time-slots or not. Therefore, the resultant crt dis-
play does not shift position as normallinvert or calluncal in-
formation is encoded by the plug-in. The end-of-word pulse
connected to pin 8 of U1080 through C1080 resets the char-
acter position counter to the first character position at the
end of each word.
The decimal point logic portion of this stage allows deci-
mal points to be added to the crt display as encoded by the
plug-in units. When row 7 is encoded in coincidence with
columns 3 through 7 (usually encoded during time-slot I), a
decimal point is placed at one of the five locations on the crt
identified in row 7 of the character selection matrix (Fig.
3-8). This instruction refers to the decimal point location in
relation to the total number of characters that can be dis-
played on the crt (see Fig. 3-1 1). For example, if column 3
and row 7 are encoded during time-slot 1, the system is
instructed to place a decimal point in location No. 3. As
shown in Fig. 3-1 1, this displays a decimal point before the
third character that can be displayed on the crt (first three
time-slots produce a space whether data is encoded or not;
see previous paragraph). The simultaneous application of
row 7 data to the Y-input of the format generator through
RlO8O raises the decimal point so it appears between the
displayed characters.
When decimal-point data is encoded, the crt is unblanked
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 character
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
Decimal-point location en-
coded during this timeslot
First number of measure-
ment normally displayed at
this location
Decimal point
location No. 7
(column 7)
Decimal point
location No. 6
location No. 3
(column 6)
Decimal point
(column 3) location No. 5
(column 5)
-
Fig. 3-11. Readout word relating 10 possible character locations
to the decimal point instructions that can be encoded, and the
resultant crt display.
the crt beam to the area of the crt that is associated with the
plug-in channel that originated the information (see Fig. 3-3).
In addition, the character position current from the deci-
mal point logic and character position stage is added to the
X (horizontal) input signal to space the characters horizon-
tally on the crt (see previous discussion). The channel
switch Off signal at pin 13 activates this stage when a char-
acter is to be displayed on the crt. The vertical spacing ad-
justment, R118, sets the separation between the upper and
lower readout displays.
Y-Output Amplifier
The Y-output signal at pin 6 of U1100 is connected to the
Y-output amplifier, Q1100. This stage provides a low imped-
ance load for the format generator while providing isolation
between the readout system and the vertical amplifier.
X-Output Amplifier
The X-output amplifier, Q1110, operates similarly to the
Y-output amplifier. It provides the horizontal deflection from
the readout signal available at pin 4 of U1100. Horizontal
position is controlled by R1110, which changes the emitter
current of Q1110.
The X and Y deflection signals, produced by the charac- Horizontal channel switch U1130 normally passes sig-
ter generator stage, are connected to pins 2 and 7, respec-
nals from the horizontal plug-in connector to the horizontal
tively, of format generator U1100. The word address code amplifier with unit gain. When the channel switch Off signal
from the word counter is also connected to pins 1, 8, and 15 is generated by timer U1000, the channel switch substitutes
of this stage. The word address code directs the format
the horizontal readout signal for the horizontal plug-in con-
generator to add current to the X and Y signals to deflect nector signal.
REV MAY 1982