Tektronix 5441 Instruction Manual page 54

Theory of Operation-5441lR5441
Fig.
3-10.
Block representation of memory sequence in
U1060.
Interrogation pulses
A
f
TimeSlot 5 TirneSlot 6 Time-Slot 8 TimeSlot 1
>
4
3
6 5
Character Generators
The character generator stage consists of five similar in-
tegrated circuits, U1090-U1098, which generate the X (hori-
zontal) and Y (vertical) outputs at pins 16 and 1,
respectively, to produce the character displayed on the crt.
Each integrated circuit can produce 10 individual characters.
U1090, which is designated as the 'numerals" character
generator, can produce the numerals 0 through 9 shown in
row 1 of the character selection matrix (Fig. 3-8). U1092 can
produce the symbols shown in row 2 of the character selec-
tion matrix and U1094 produces the prefixes and some let-
ters of the alphabet that are used as prefixes in row 4.
U1096 and U1098 produce the remaining letters of the al-
phabet shown in rows 5 and 6 of the character selection
matrix. All of the character-generator stages receive the col-
umn digital data from column decoder U1070 in parallel.
However, only one of the character generators receives row
data at a particular time and only the stage that receives
both row and column data is activated. For example, if col-
umn 2 is encoded by a plug-in unit, the five character gener-
ators are enabled so that either a 1,
<,
p,
V, or N can be
produced. However, if at the same time row 4 has also been
A A
Column 1 12
+
d
(Add '0')
-
Memory
Column 2 13
A
L
B
-
-
-
(Add '0')
<
encoded by the plug-in unit, only the prefix character gener-
ator U1094 will produce an output, to result in a
p
displayed
on the screen. This integrated circuit provides current out-
puts to the format generator, which produce the selected
character on the crt. In a similar manner, any of the 50 char-
acters shown in the character selectin matrix can be dis-
played by correct addressing of the row and column.
(Blank)
Row 3
16
< - -
Enable to all memories
Word Trigger 9
< - '
Reset to all memories
A
4
4
t
4
t
Decimal Point Logic and Character Position
Counter
. I
7
4 t
I
1
Decimal point logic and character position counter U1080
performs two functions. The first function is to produce a
staircase current, which is added to the X (horizontal) signal
to space the characters horizontally on the crt. After each
character is generated the negative-going edge of the chan-
nel switch Off signal at pin 5 advances the character posi-
tion counter. This produces a current step output at pin 3,
which, when added to the X signal, causes the next charac-
ter to be displayed one character space to the right. This
stage can also be advanced when a space instruction is
encoded by the plug-in unit, so that a space is left between
t ,
3-18
REV MAY 1982
Column 3 10
=
Column 4 11
r
Memory
C
(Reduce
'
prefix)
-
.
:
t
1
L
Column 1 0 14
r
Memory
D