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Controller PCB
3-6
The character code (or special-character code) indicates to the character generator
which of the 256 possible characters to display in a given display position. Also
associated with each display position is an attribute code, which requires the third
byte of data. The attribute code specifies the absence or presence of eight possible
character supplements, which are shown in Table 3-1 and Figure 3-5.
Table 3-1 Attribute Description for Character Attribute Code
ATTRIBUTE
FUNCTION
COMMENT
GR
Green
Must always equal '1' with
monochrome display.
BU
Blue
Character is blue.
R/H
Redl
Red color (color display)/high-
highlight
lighted character (monochrome).
RV
Reverse
Character and Field Video
video
transposed.
BL
Blinking
VB
Vertical bar
OB
Over-bar
UB
Under-bar
GR, R/H,
Nullify
No character displayed.
and BU
(secret)
all equal '0'
BIT NUMBER
7
6
5
4
3
2
1
0
ATTRIBUTE CODE
I
GR
I
BU
I
R/H
I
RV
I
BL
VB lOB
I
UB
I
Figure 3-5 Bit Map for Character Attribute Code
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