c)
Example
of
CPU
read/write access
• Shown next are access examples
of
REPlACE write,
PSET
write, and
SEARCH
read in the 320 x 200,
16-color mode.
As
for
display colors, Plane I corresponds
to
8,
II
to
R,
Ill
to
G,
and
IV
to
I.
CD
REPlACE write
• To develop
light
yellow
characters on the graphic
screen.
Plane I
(B)
data
Plane
11
(R)
data
V
R
I o I o I o I o I , I , I , I ,
Display before
write
A
M
lt develops the screen when a next
CG
patterns are
written after setting the REPlACE mode and the
light
yellow calor in the
WF
register.
Mode B/A Color designation
Plane
Ill
(G)
data Plane
IV
(I) data
So, the bit
"1"
of
the write data becomes the calor
specified by
WF
and rest
of
others become
RESET
(black).
WF
register I 1 o o I o I 1 o I : Light
yellow
replace mode
0
0
0
Write data I
(CG
pattern)
0
L-----------------~
Plane I
Plane
ll
V
I o I o I o I o I o I o I o I o I
I
0
I ,
o I , I o I
, I o I
, I
R
A
M
Display after
write
I o I ,
@
PSET
write
• To overlay a
light
yellow
hatching over the graphic
display screen
of
G).
0
Plane
Ill
Plane
IV
I , I o I , I o i , I
I
o I , I o I , I o I ,
I o I ,
Mode B/A Color designation
WF register
I 1 o I o I 1 0 I Light
yellow
PSET
mode
G R B
Write data 0
0 0
0
, I
I
(B)
11
(R)
V
lololololt
lol
, I o I
I
o I ,
I,
I , I o I , I , I , I
R
A
Display after
write
M
I o I ,
I,
So,
only
the bit
"1"
of
the
write
data becomes the
calor
specified by WF in
this
mode, and rest
of
other
colors do not change.
@
SEARCH
read +
PSET
write
• To change
light
yellow
in@
above
to
change
to
red
• The
following
data are set when
the
memory
is read
after setting the
light
yellow
search mode in the
RF
register.
Mode
BIA
Col
or
designation
RF
register
LI_,__L_
__
_j_l_o---'-l_,
____
o__,l:
Light
yellow
search
21
Ill
(G)
IV
(I)
I,
I , I ,
0
I,
I 0
I,
I o I
, I
0 I ,
I o I , I
Read
data 0 0 0 o t I : Only the
bit
of
light
yellow
c__
_________
___J
becomes
"1
".
• When the above read data are read after setting the
red
PSET
mode in the
WR
register.
Now, a partial calor change has been attained.
As in
above, it enhances fast display change
with
less
of
VRAM accessing by using various
write
modes.
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