Ascii c.g. structure – Sharp MZ-3500 User Manual
Page 40
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4
8 CG Address Select Circuit
ASCII C.G. Structure
1020
1011-
leBytes
ifiBytes
1000
OM-I-
0020
001
h
8 Bytes
0018
0017
8 Bytes
0010
m
1
8 Bytes
0 I0>'
0 K)
8 Bytes
N
Character
Code 01
For
Model 3500
Character
Code 00
For
t
Model 3500
1
\11 /
M^-0 ^
]
Code 01
f
For
' >
Model 3200 A3=l
♦
^ Code 01 i
T
- For <
, Model 3500; \ 1-0
Character
Code 00
For
1
Model 3200 \ -i 1
/ Character ’
" Code 00 ill
T
^ For <
.Model 3500' \ 1
8x16 dot
Pattern
400 Rasters
8x8 Dot
Pattern
200 Rasters
A
ASCII character structure
of the 200 raster CRT
ASCII character structure
of the 400 raster CRT
[Circuit description]
(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 circuit 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
sets A12 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 input 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
2
When the 200 raster CRT is in use, RA40 is set turned to low level
which sets A12 of the CG to low level continuously, so that the CG
address
0000 OF FF is selected Also, gate (2) is opened so that the
CPU
8 b IS
-