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MZ3500
(Subroutine
lo
send
command
and
parameter
to the GDC
via
the
FIFO)
HL reg —
First
address
of the
command code
oarametpr
B. reg —
Q'ty
of
data.
C
reg - 60H
(graphic GDC),
70H
(character GDC)
>
FIFO
Empty?
;
COMMAND
—• GDC
;
Return
if
parameter
not
sent.
f
FIFO
Empty?
;
PARAMETER
—
GDC
;
Return when
all
parameters
were
sent.
RET
Example
of
graphic
drawing
by GDC
1)
Dot
display
0000
0028
0001
0027
VRAM
16-bit
structure
Example
to
display
a dot on the
fourth
bit of the
address
CSRW
C 49H
-COMMAND
CODE
P1
01H — Low
order
one
byte
of the ab-
solute
address
P2
OOH —
High
order
one
byte
of thp ah
solute
address
P3
30H - Dot
address
(dAD)
WRITE
C 23H -
COMMAND
CODE
VECTE
C 6CH -
COMMAND CODE
-
49-