Radio Shack TRS-80 Service Manual page 18

Control Register Bits
D6 D5 D4
CSS A*/G GMD
0 0 X
0 0 X
1 0 X
1 0 X
X 0 X
VDG
COLOR
PINS
CSS INV Character Color Background Border
0 Green Black
0
1 Black Green
0 Orange Black
0
1 Black Orange
Lx C2 C1 C0 Color
0 x x x Black
1 0 0 0 Green
1 0 0 1 Yellow
1 0 1 0 Blue
x
x
1 0 1 1 Red
1 1 0 0 Buff
1 1 0 1 Cyan
1 1 1 0 Magenta
1 1 1 1 Orange
0 1 2
0 - - -
1 - - -
SPACE
2 ! "
BAR
3 0 1 2
4 @ A B
5 P Q R
6
@
A B
7
P Q R
-
Table 2. VDG Control Register
D3 D2
GM1 GM2
(INT*/EXT)
X 0
X 0
X 0
X 0
X 0
TV SCREEN
Display Mode
32 Characters
Black
in columns
16 Characters
Black
in rows
64 Display elements
in columns
Black
32 Display elements
in rows
Table 4. AVAILABLE CHARACTERS (00 - 7F)
3 4 5 6
- - - -
- - - -
# $ % &
3 4 5 6
C D E F
S T U V
C D E F
S T U V
= INVERTED CHARACTER
= UNDEFINED
DMA Bits
D6 D7
INV A*/S
0 0 Alphanumerical green
1 0 Alphanumerical inverted green
0 0 Alphanumerical orange
1 0 Alphanumerical inverted orange
X 1 Semigraphics Four
Table 3
VDG DATA BUS
Detail
8 dots
I N
12 dots
7
0
V
ASCII code
5
L L
3 2
1 C C C L L L L
2 1 0 3 2 1 0
one
L L
1 0
element
7 8 9
- - -
- - -
' ( )
7 8 9
G H I
W X Y
G H I
W X Y
– 18 –
Mode Selected
COMMENTS
The ALPHANUMERIC INTERNAL mode
uses an internal character generator which
contains the following five dot by seven
dot characters @ A B C D E F G H I J K L
M N O P Q R S T U V W X Y Z [ \ ] ➡ ➟
SP ! " # $ % & ' ( ) * + , - . / 0 1 2 3 4 5 6 7 8
9 : ; < = > ?
The SEMIGRAPHICS FOUR mode uses
an internal "coarse graphics" generator
in which a rectangle (eight dots by twelve
dots) is divided into four equal parts. The
luminance of each part is determined by
a corresponding bit on the VDG data bus.
The color of illummated parts is determined
by three bits. It requires 512 bytes of
display memory.
A B C D
- - - -
- - - -
* + , -
: ; < =
J K L M
Z [ \ ]
J K L M
[ ]
Z \
E F
- -
- -
. /
> ?
N O
➡ ➟
N O
➡
➟