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4 8 CG Address Select Circuit
A4 -All
~
.. I\
1\,(
nu,
r-__________________
~R~a~st~e~r~s~O~
_______
1~0~R~as~t~e~rs~I
______
~k~\4~O~1\12
Mask ROM
f< \
111
1 10Rasters
I
IORasters
(l
When 400 rasters In use
Ild
~-.------------------------------~--_4~--~--\~<~'--------------~
L,ne counter
PO
I
1>8
3
~
()'-
'"10.>00
()I I
MI
oOH
When 200 Raster
Goes low once par 16 bytes
' I l4 ~-+--------------------------4
Neagatlve
LIne Counter
I I I
ASCII C.G. Structure
• 11
~ ~
L::::==:::J
102()
101
~
16Byte
loo~
I"Byte
1000
O~H
0020
001
~
s
s
8
Bytes
OOIH
nOli
H
Bytes
()(JIIJ
{VI( I
K
Bytes
k
Bytes
flJ
-
.----
Character
Code 01
For
Model 3500
Character
Code 00
For
Model 3500
r--
Code 01
For
Model 3200
~ Co~e
/ /
01
For
Model 3500
Character
Code 00
For
Model 3200
Character
Code 00
For
Model 3500
i
\ 1)= I
\ )?-o
1
i
A3=1
i
\ <-0
i
\ l
I
i
\ j
8 x 16 dot
Pattern
400 Rasters
8
x
8 Dot
Pattern
200 Rasters
Goes hIgh per
400 raster
1I
When 200 rasters on ASCII In use
(only the hIgh order 8 bytes of 16 bytes are set to low level)
ASCII character structure
of the 200 raster CRT
ASCII character structure
of the 400 raster CRT
[CircuIt descrtptlon]
(Purpose)
The character genrerator (CG) Incorporates all character code" used by
the 200 raster VIdeo display unIt of the YX 3500 and by the 400 raster
Video display unit of the YX 3500 The CG address select ClfrlJlt IS
therefore used to select those modes
{Operational description]
1 When the 400 raster CRT IS In use, RA40 IS set to high level which
2
sets A 12 of the CG to high level at all times, so that the CG address
above 1000 IS selected Also, gate (1) opened so that LC3 IS IlllJut to
A3 of the CG At the same time, gate (3) IS opened so that the gate
of the LS240 IS closed every 16 bytes
When the 200 raster CRT IS
In
use, RA40 IS set turned to low level
wh Ich sets A 12 of the CG to low level continuously, so that the CG
address
0000 OF F F
IS selected Also, gate
(2)
IS opened so that the
CPU
-
4')-
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