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MZ3500
4-12. Read/write
from
the
Z-80
to
V-RAM
Read/write
of the
Model
3500
V-RAM
is
done
via the
UPD7220GDC. There
are two
methods used
to
read/write
data.
The
method
(1) is
used
for the
model
3500.
(1)
Read/write
via the 16
byte FIFO.
(2)
Read/write
of
V-RAM
in the DMA
mode
without
intervention
of the
FIFO.
(Outline
of the
read/write data
via the
FIFO;
NO
YES
Set
GDC
command
code
YES
Set
parameter
for the
command
YES
Set
parameter
for the
command.
I
Method
used
to
give
a
command
to the
GDC.
Command
must
be
given
to the GDC in the
same
manner.
On
next
page
is the
program
of the
above
flowchart.
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48-