Hitachi MB-6890, Service Manual

Page: 58 / 123

6-4-7 Display address conversion switch circuit
‘
Basic Master L-3 has normal mode and
In high
resolution
mode,
1 character
circuit.
In fig. 6-16 circuit, HRSO
IC5l
and L
level is
outputted to
the
display address 4 bit
MA13-MA10
from
output
of IC4O
without
conversion
in
In
high
resolution
mode, HRSO-SW
=
L
high
resolution
mode
as
display
mode.
is divided
by
8
to
the
raster
direction
circuit is the display
shows the
main
part
of the
is
inputted to G
input of
of C5l. Therefore,
upper
the CRTC is still connected
to
the
display address
as
shown in
fig.
6-17.
and
make
one
character
with
8 byte address.
This
address conversion and switch circuit.
Fig.
6-l6
SW
="H"level
output
lY-4Y
level is inputted
to
E
input of IC5l,
tha
raster
address
RAA1-RAA3
as
shown at fig.
6-9
are
outputted to
the each
output
lY-4?
of
IC5l
by character display mode signal (by inputting SELECT
pin of IC5l).
By
this
raster
address
RAA1-RAA3,
upper
4bit
MA13-MA10
display address
is
converted to
MAA13’MAA10.
Fig. 6-18 shows the 40 characters and
BO
characters
high
resolution
mode
CRT address.
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